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I try to make a fit of my curve. My raw data is in an xlsx file. I extract them using pandas. I want to do two different fit because there is a change in behavior from Ra = 1e6. We know that Ra is proportional to Nu**a. a = 0.25 for Ra <1e6 and if not a = 0.33.
import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
from math import log10
from scipy.optimize import curve_fit
import lmfit
data=pd.read_excel('data.xlsx',sheet_name='Sheet2',index=False,dtype={'Ra': float})
print(data)
plt.xscale('log')
plt.yscale('log')
plt.scatter(data['Ra'].values, data['Nu_top'].values, label='Nu_top')
plt.scatter(data['Ra'].values, data['Nu_bottom'].values, label='Nu_bottom')
plt.errorbar(data['Ra'].values, data['Nu_top'].values , yerr=data['Ecart type top'].values, linestyle="None")
plt.errorbar(data['Ra'].values, data['Nu_bottom'].values , yerr=data['Ecart type bot'].values, linestyle="None")
def func(x,a):
return 10**(np.log10(x)/a)
"""maxX = max(data['Ra'].values)
minX = min(data['Ra'].values)
maxY = max(data['Nu_top'].values)
minY = min(data['Nu_top'].values)
maxXY = max(maxX, maxY)
parameterBounds = [-maxXY, maxXY]"""
from lmfit import Model
mod = Model(func)
params = mod.make_params(a=0.25)
ret = mod.fit(data['Nu_top'].head(10).values, params, x=data['Ra'].head(10).values)
print(ret.fit_report())
popt, pcov = curve_fit(func, data['Ra'].head(10).values,
data['Nu_top'].head(10).values, sigma=data['Ecart type top'].head(10).values,
absolute_sigma=True, p0=[0.25])
plt.plot(data['Ra'].head(10).values, func(data['Ra'].head(10).values, *popt),
'r-', label='fit: a=%5.3f' % tuple(popt))
popt, pcov = curve_fit(func, data['Ra'].tail(4).values, data['Nu_top'].tail(4).values,
sigma=data['Ecart type top'].tail(4).values,
absolute_sigma=True, p0=[0.33])
plt.plot(data['Ra'].tail(4).values, func(data['Ra'].tail(4).values, *popt),
'b-', label='fit: a=%5.3f' % tuple(popt))
print(pcov)
plt.grid
plt.title("Nusselt en fonction de Ra")
plt.xlabel('Ra')
plt.ylabel('Nu')
plt.legend()
plt.show()
So I use the log: logRa = a * logNu.
Ra = x axis
Nu = y axis
That's why I defined my function func in this way.
my two fit are not all correct as you can see. I have a covariance equal to [0.00010971]. So I had to do something wrong but I don't see it. I need help please.
Here the data file:
data.xlsx
I noticed that the data values for Ra are large, and after scaling them I performed an equation search - here is my result with code. I use the standard scipy genetic algorithm module differential_evolution to determine initial parameter values for curve_fit(), and that module uses the Latin Hypercube algorithm to ensure a thorough search of parameter space which requires bounds within which to search. It is much easier to give ranges for the initial parameter estimates than to find specific values. This equation works well for both nu_top and nu_bottom, note that the plots are not log scaled as it is unnecessary in this example.
import numpy, scipy, matplotlib
import matplotlib.pyplot as plt
from scipy.optimize import curve_fit
from scipy.optimize import differential_evolution
import pandas
import warnings
filename = 'data.xlsx'
data=pandas.read_excel(filename,sheet_name='Sheet2',index=False,dtype={'Ra': float})
# notice the Ra scaling by 10000.0
xData = data['Ra'].values / 10000.0
yData = data['Nu_bottom']
def func(x, a, b, c): # "Combined Power And Exponential" from zunzun.com
return a * numpy.power(x, b) * numpy.exp(c * x)
# function for genetic algorithm to minimize (sum of squared error)
def sumOfSquaredError(parameterTuple):
warnings.filterwarnings("ignore") # do not print warnings by genetic algorithm
val = func(xData, *parameterTuple)
return numpy.sum((yData - val) ** 2.0)
def generate_Initial_Parameters():
# min and max used for bounds
maxX = max(xData)
minX = min(xData)
maxY = max(yData)
minY = min(yData)
parameterBounds = []
parameterBounds.append([0.0, 10.0]) # search bounds for a
parameterBounds.append([0.0, 10.0]) # search bounds for b
parameterBounds.append([0.0, 10.0]) # search bounds for c
# "seed" the numpy random number generator for repeatable results
result = differential_evolution(sumOfSquaredError, parameterBounds, seed=3)
return result.x
# by default, differential_evolution completes by calling curve_fit() using parameter bounds
geneticParameters = generate_Initial_Parameters()
# now call curve_fit without passing bounds from the genetic algorithm,
# just in case the best fit parameters are aoutside those bounds
fittedParameters, pcov = curve_fit(func, xData, yData, geneticParameters)
print('Fitted parameters:', fittedParameters)
print()
modelPredictions = func(xData, *fittedParameters)
absError = modelPredictions - yData
SE = numpy.square(absError) # squared errors
MSE = numpy.mean(SE) # mean squared errors
RMSE = numpy.sqrt(MSE) # Root Mean Squared Error, RMSE
Rsquared = 1.0 - (numpy.var(absError) / numpy.var(yData))
print()
print('RMSE:', RMSE)
print('R-squared:', Rsquared)
print()
##########################################################
# graphics output section
def ModelAndScatterPlot(graphWidth, graphHeight):
f = plt.figure(figsize=(graphWidth/100.0, graphHeight/100.0), dpi=100)
axes = f.add_subplot(111)
# first the raw data as a scatter plot
axes.plot(xData, yData, 'D')
# create data for the fitted equation plot
xModel = numpy.linspace(min(xData), max(xData))
yModel = func(xModel, *fittedParameters)
# now the model as a line plot
axes.plot(xModel, yModel)
axes.set_xlabel('X Data') # X axis data label
axes.set_ylabel('Y Data') # Y axis data label
plt.show()
plt.close('all') # clean up after using pyplot
graphWidth = 800
graphHeight = 600
ModelAndScatterPlot(graphWidth, graphHeight)
Here I put my data x and y in log10 (). The graph is in log scale. So normally I should have two affine functions with a coefficient of 0.25 and 0.33. I change the function func in your program James and bounds for b and c but I have no good result.
import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
from math import log10, log
from scipy.optimize import curve_fit
import lmfit
data=pd.read_excel('data.xlsx',sheet_name='Sheet2',index=False,dtype={'Ra': float})
print(data)
plt.xscale('log')
plt.yscale('log')
plt.scatter(np.log10(data['Ra'].values), np.log10(data['Nu_top'].values), label='Nu_top')
plt.scatter(np.log10(data['Ra'].values), np.log10(data['Nu_bottom'].values), label='Nu_bottom')
plt.errorbar(np.log10(data['Ra'].values), np.log10(data['Nu_top'].values) , yerr=data['Ecart type top'].values, linestyle="None")
plt.errorbar(np.log10(data['Ra'].values), np.log10(data['Nu_bottom'].values) , yerr=data['Ecart type bot'].values, linestyle="None")
def func(x,a):
return a*x
maxX = max(data['Ra'].values)
minX = min(data['Ra'].values)
maxY = max(data['Nu_top'].values)
minY = min(data['Nu_top'].values)
maxXY = max(maxX, maxY)
parameterBounds = [-maxXY, maxXY]
from lmfit import Model
mod = Model(func)
params = mod.make_params(a=0.25)
ret = mod.fit(np.log10(data['Nu_top'].head(10).values), params, x=np.log10(data['Ra'].head(10).values))
print(ret.fit_report())
popt, pcov = curve_fit(func, np.log10(data['Ra'].head(10).values), np.log10(data['Nu_top'].head(10).values), sigma=data['Ecart type top'].head(10).values, absolute_sigma=True, p0=[0.25])
plt.plot(np.log10(data['Ra'].head(10).values), func(np.log10(data['Ra'].head(10).values), *popt), 'r-', label='fit: a=%5.3f' % tuple(popt))
popt, pcov = curve_fit(func, np.log10(data['Ra'].tail(4).values), np.log10(data['Nu_top'].tail(4).values), sigma=data['Ecart type top'].tail(4).values, absolute_sigma=True, p0=[0.33])
plt.plot(np.log10(data['Ra'].tail(4).values), func(np.log10(data['Ra'].tail(4).values), *popt), 'b-', label='fit: a=%5.3f' % tuple(popt))
print(pcov)
plt.grid
plt.title("Nusselt en fonction de Ra")
plt.xlabel('log10(Ra)')
plt.ylabel('log10(Nu)')
plt.legend()
plt.show()
With polyfit I have better results.
With my code I open the file and I calculate log (Ra) and log (Nu) then plot (log (Ra), log (Nu)) in log scale.
I'm supposed to have a = 0.25 for Ra <1e6 and if not a = 0.33
import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
from math import log10
from numpy import polyfit
import numpy.polynomial.polynomial as poly
data=pd.read_excel('data.xlsx',sheet_name='Sheet2',index=False,dtype={'Ra': float})
print(data)
x=np.log10(data['Ra'].values)
y1=np.log10(data['Nu_top'].values)
y2=np.log10(data['Nu_bottom'].values)
x2=np.log10(data['Ra'].head(11).values)
y4=np.log10(data['Nu_top'].head(11).values)
x3=np.log10(data['Ra'].tail(4).values)
y5=np.log10(data['Nu_top'].tail(4).values)
plt.xscale('log')
plt.yscale('log')
plt.scatter(x, y1, label='Nu_top')
plt.scatter(x, y2, label='Nu_bottom')
plt.errorbar(x, y1 , yerr=data['Ecart type top'].values, linestyle="None")
plt.errorbar(x, y2 , yerr=data['Ecart type bot'].values, linestyle="None")
"""a=np.ones(10, dtype=np.float)
weights = np.insert(a,0,1E10)"""
coefs = poly.polyfit(x2, y4, 1)
print(coefs)
ffit = poly.polyval(x2, coefs)
plt.plot(x2, ffit, label='fit: b=%5.3f, a=%5.3f' % tuple(coefs))
absError = ffit - x2
SE = np.square(absError) # squared errors
MSE = np.mean(SE) # mean squared errors
RMSE = np.sqrt(MSE) # Root Mean Squared Error, RMSE
Rsquared = 1.0 - (np.var(absError) / np.var(x2))
print('RMSE:', RMSE)
print('R-squared:', Rsquared)
print()
print('Predicted value at x=0:', ffit[0])
print()
coefs = poly.polyfit(x3, y5, 1)
ffit = poly.polyval(x3, coefs)
plt.plot(x3, ffit, label='fit: b=%5.3f, a=%5.3f' % tuple(coefs))
plt.grid
plt.title("Nusselt en fonction de Ra")
plt.xlabel('log10(Ra)')
plt.ylabel('log10(Nu)')
plt.legend()
plt.show()
My problem is solved, I managed to fit my curves with more or less correct results
I want to append HoG feature vectors to an empty matrix of unknown dimension. Is it required to specify the dimension of the matrix in advance? I have tried some code in python but it says all the input arrays must have same dimension.
import matplotlib.pyplot as plt
from skimage.feature import hog
from skimage import data, exposure, img_as_float
from skimage import data
import numpy as np
from scipy import linalg
import cv2
import glob
shape = (16576, 1)
X = np.empty(shape)
print X.shape
hog_image = np.empty(shape)
hog_image_rescaled = np.empty(shape)
for img in glob.glob("/home/madhuri/pythoncode/faces/*.jpg"):
n= cv2.imread(img)
gray = cv2.cvtColor(n, cv2.COLOR_RGB2GRAY)
hog_image = hog(gray, orientations=9, pixels_per_cell=(16, 16),
cells_per_block=(3, 3), visualise=False)
hog_image_rescaled = exposure.rescale_intensity(hog_image,
in_range=(0,10))
X = np.append(X, hog_image_rescaled, axis=1)
print 'X is'
print np.shape(X)
X = [] # use an 'empty' list
# hog_image = np.empty(shape) # no point initializing these variables
# hog_image_rescaled = np.empty(shape) # you just reassign them in the loop
for img in glob.glob("/home/madhuri/pythoncode/faces/*.jpg"):
n= cv2.imread(img)
gray = cv2.cvtColor(n, cv2.COLOR_RGB2GRAY)
hog_image = hog(gray, orientations=9, pixels_per_cell=(16, 16),
cells_per_block=(3, 3), visualise=False)
hog_image_rescaled = exposure.rescale_intensity(hog_image,
in_range=(0,10))
X.append(hog_image_rescaled)
Now X will be a list of rescaled images. Those elements can now be concatenated on which ever dimension is appropriate:
np.concatenate(X, axis=1)
np.stack(X)
# etc
The list model of
alist = []
for ....
alist.append(...)
does not translate well to arrays. np.append is a cover for np.concatenate, and makes a new array, which is more expensive than list append. And defining a good starting 'empty' array for such a loop is tricky. np.empty is not appropriate:
In [977]: np.empty((2,3))
Out[977]:
array([[1.48e-323, 1.24e-322, 1.33e-322],
[1.33e-322, 1.38e-322, 1.38e-322]])
In [978]: np.append(_, np.zeros((2,1)), axis=1)
Out[978]:
array([[1.48e-323, 1.24e-322, 1.33e-322, 0.00e+000],
[1.33e-322, 1.38e-322, 1.38e-322, 0.00e+000]])
I'm trying to implement a simple Bayesian Inference using a ODE model. I want to use the NUTS algorithm to sample but it gives me an initialization error. I do not know much about the PyMC3 as I'm new to this. Please take a look and tell me what is wrong.
import numpy as np
import matplotlib.pyplot as plt
from scipy.integrate import odeint
import seaborn
import pymc3 as pm
import theano.tensor as T
from theano.compile.ops import as_op
#Actual Solution of the Differential Equation(Used to generate data)
def actual(a,b,x):
Y = np.exp(-b*x)*(a*np.exp(b*x)*(b*x-1)+a+b**2)/b**2
return Y
#Method For Solving the ODE
def lv(xdata, a=5.0, b=0.2):
def dy_dx(y, x):
return a*x - b*y
y0 = 1.0
Y, dict = odeint(dy_dx,y0,xdata,full_output=True)
return Y
#Generating Data for Bayesian Inference
a0, b0 = 5, 0.2
xdata = np.linspace(0, 21, 100)
ydata = actual(a0,b0,xdata)
# Adding some error to the ydata points
yerror = 10*np.random.rand(len(xdata))
ydata += np.random.normal(0.0, np.sqrt(yerror))
ydata = np.ravel(ydata)
#as_op(itypes=[T.dscalar, T.dscalar], otypes=[T.dvector])
def func(al,be):
Q = lv(xdata, a=al, b=be)
return np.ravel(Q)
# Number of Samples and Initial Conditions
nsample = 5000
y0 = 1.0
# Model for Bayesian Inference
model = pm.Model()
with model:
# Priors for unknown model parameters
alpha = pm.Uniform('alpha', lower=a0/2, upper=a0+a0/2)
beta = pm.Uniform('beta', lower=b0/2, upper=b0+b0/2)
# Expected value of outcome
mu = func(alpha,beta)
# Likelihood (sampling distribution) of observations
Y_obs = pm.Normal('Y_obs', mu=mu, sd=yerror, observed=ydata)
trace = pm.sample(nsample, nchains=1)
pm.traceplot(trace)
plt.show()
The error that I get is
Auto-assigning NUTS sampler...
Initializing NUTS using jitter+adapt_diag...
Initializing NUTS failed. Falling back to elementwise auto-assignment.
Any help would be really appreciated
I am plotting a choropleth map using geopandas and I need to plot a customized tabular legend. This question's answer shows how to obtain a tabular legend for a contourf plot.
And I'am using it in the code bellow :
import pandas as pd
import pysal as ps
import geopandas as gp
import numpy as np
import matplotlib.pyplot as plt
pth = 'outcom.shp'
tracts = gp.GeoDataFrame.from_file(pth)
ax = tracts.plot(column='Density', scheme='QUANTILES')
valeur = np.array([.1,.45,.7])
text=[["Faible","Ng<1,5" ],["Moyenne","1,5<Ng<2,5"],[u"Elevee", "Ng>2,5"]]
colLabels = ["Exposition", u"Densite"]
tab = ax.table(cellText=text, colLabels=colLabels, colWidths = [0.2,0.2], loc='lower right', cellColours=plt.cm.hot_r(np.c_[valeur,valeur]))
plt.show()
And here's the result i get :
So basically, as you can see there is no link between the colors of the classes in the map and the table. I need to have the exact colors that i have in the table shown in the map. The 'NG value' shown in the legend should be extracted from the column 'DENSITY' that i am plotting.
However, since I do not have a contour plot to extract the colormap from, I'm lost on how to link the tabular legend and the map's colors.
Note: This answer is outdated. Modern geopandas allows to use a normal legend via legend=True argument. I still keep it here for reference though, or in case someone wants a truely tabular legend.
The geopandas plot does not support adding a legend. It also does not provide access to its plotting object and only returns an axes with the shapes as polygons. (It does not even provide a PolyCollection to work with). It is therefore a lot of tedious work to create a normal legend for such a plot.
Fortunately some of this work is already beeing done in the example notebook Choropleth classification with PySAL and GeoPandas - With legend
So we need to take this code and implement the custom tabular legend which comes from this answer.
Here is the complete code:
def __pysal_choro(values, scheme, k=5):
""" Wrapper for choropleth schemes from PySAL for use with plot_dataframe
Parameters
----------
values
Series to be plotted
scheme
pysal.esda.mapclassify classificatin scheme ['Equal_interval'|'Quantiles'|'Fisher_Jenks']
k
number of classes (2 <= k <=9)
Returns
-------
values
Series with values replaced with class identifier if PySAL is available, otherwise the original values are used
"""
try:
from pysal.esda.mapclassify import Quantiles, Equal_Interval, Fisher_Jenks
schemes = {}
schemes['equal_interval'] = Equal_Interval
schemes['quantiles'] = Quantiles
schemes['fisher_jenks'] = Fisher_Jenks
s0 = scheme
scheme = scheme.lower()
if scheme not in schemes:
scheme = 'quantiles'
print('Unrecognized scheme: ', s0)
print('Using Quantiles instead')
if k < 2 or k > 9:
print('Invalid k: ', k)
print('2<=k<=9, setting k=5 (default)')
k = 5
binning = schemes[scheme](values, k)
values = binning.yb
except ImportError:
print('PySAL not installed, setting map to default')
return binning
def plot_polygon(ax, poly, facecolor='red', edgecolor='black', alpha=0.5, linewidth=1):
""" Plot a single Polygon geometry """
from descartes.patch import PolygonPatch
a = np.asarray(poly.exterior)
# without Descartes, we could make a Patch of exterior
ax.add_patch(PolygonPatch(poly, facecolor=facecolor, alpha=alpha))
ax.plot(a[:, 0], a[:, 1], color=edgecolor, linewidth=linewidth)
for p in poly.interiors:
x, y = zip(*p.coords)
ax.plot(x, y, color=edgecolor, linewidth=linewidth)
def plot_multipolygon(ax, geom, facecolor='red', edgecolor='black', alpha=0.5, linewidth=1):
""" Can safely call with either Polygon or Multipolygon geometry
"""
if geom.type == 'Polygon':
plot_polygon(ax, geom, facecolor=facecolor, edgecolor=edgecolor, alpha=alpha, linewidth=linewidth)
elif geom.type == 'MultiPolygon':
for poly in geom.geoms:
plot_polygon(ax, poly, facecolor=facecolor, edgecolor=edgecolor, alpha=alpha, linewidth=linewidth)
import numpy as np
from geopandas.plotting import (plot_linestring, plot_point, norm_cmap)
def plot_dataframe(s, column=None, colormap=None, alpha=0.5,
categorical=False, legend=False, axes=None, scheme=None,
k=5, linewidth=1):
""" Plot a GeoDataFrame
Generate a plot of a GeoDataFrame with matplotlib. If a
column is specified, the plot coloring will be based on values
in that column. Otherwise, a categorical plot of the
geometries in the `geometry` column will be generated.
Parameters
----------
GeoDataFrame
The GeoDataFrame to be plotted. Currently Polygon,
MultiPolygon, LineString, MultiLineString and Point
geometries can be plotted.
column : str (default None)
The name of the column to be plotted.
categorical : bool (default False)
If False, colormap will reflect numerical values of the
column being plotted. For non-numerical columns (or if
column=None), this will be set to True.
colormap : str (default 'Set1')
The name of a colormap recognized by matplotlib.
alpha : float (default 0.5)
Alpha value for polygon fill regions. Has no effect for
lines or points.
legend : bool (default False)
Plot a legend (Experimental; currently for categorical
plots only)
axes : matplotlib.pyplot.Artist (default None)
axes on which to draw the plot
scheme : pysal.esda.mapclassify.Map_Classifier
Choropleth classification schemes
k : int (default 5)
Number of classes (ignored if scheme is None)
Returns
-------
matplotlib axes instance
"""
import matplotlib.pyplot as plt
from matplotlib.lines import Line2D
from matplotlib.colors import Normalize
from matplotlib import cm
if column is None:
raise NotImplementedError
#return plot_series(s.geometry, colormap=colormap, alpha=alpha, axes=axes)
else:
if s[column].dtype is np.dtype('O'):
categorical = True
if categorical:
if colormap is None:
colormap = 'Set1'
categories = list(set(s[column].values))
categories.sort()
valuemap = dict([(j, v) for (v, j) in enumerate(categories)])
values = [valuemap[j] for j in s[column]]
else:
values = s[column]
if scheme is not None:
binning = __pysal_choro(values, scheme, k=k)
values = binning.yb
# set categorical to True for creating the legend
categorical = True
binedges = [binning.yb.min()] + binning.bins.tolist()
categories = ['{0:.2f} - {1:.2f}'.format(binedges[i], binedges[i+1]) for i in range(len(binedges)-1)]
cmap = norm_cmap(values, colormap, Normalize, cm)
if axes == None:
fig = plt.gcf()
fig.add_subplot(111, aspect='equal')
ax = plt.gca()
else:
ax = axes
for geom, value in zip(s.geometry, values):
if geom.type == 'Polygon' or geom.type == 'MultiPolygon':
plot_multipolygon(ax, geom, facecolor=cmap.to_rgba(value), alpha=alpha, linewidth=linewidth)
elif geom.type == 'LineString' or geom.type == 'MultiLineString':
raise NotImplementedError
#plot_multilinestring(ax, geom, color=cmap.to_rgba(value))
# TODO: color point geometries
elif geom.type == 'Point':
raise NotImplementedError
#plot_point(ax, geom, color=cmap.to_rgba(value))
if legend:
if categorical:
rowtitle = ["Moyenne"] * len(categories)
rowtitle[0] = "Faible"; rowtitle[-1] = u"Elevée"
text=zip(rowtitle, categories)
colors = []
for i in range(len(categories)):
color = list(cmap.to_rgba(i))
color[3] = alpha
colors.append(color)
colLabels = ["Exposition", u"Densité"]
tab=plt.table(cellText=text, colLabels=colLabels,
colWidths = [0.2,0.2], loc='upper left',
cellColours=zip(colors, colors))
else:
# TODO: show a colorbar
raise NotImplementedError
plt.draw()
return ax
if __name__ == "__main__":
import pysal as ps
import geopandas as gp
import matplotlib.pyplot as plt
pth = ps.examples.get_path("columbus.shp")
tracts = gp.GeoDataFrame.from_file(pth)
ax = plot_dataframe(tracts, column='CRIME', scheme='QUANTILES', k=5, colormap='OrRd', legend=True)
plt.show()
resulting in the following image:
your problem is in cmap :
ax = tracts.plot(......scheme='QUANTILES',cmap='jet')
and :
tab = ...... cellColours=plt.cm.jet(np.c_[valeur,valeur]))
I have this signal :
from math import*
Fs=8000
f=500
sample=16
a=[0]*sample
for n in range(sample):
a[n]=sin(2*pi*f*n/Fs)
How can I plot a graph (this sine wave)?
and create name of xlabel as 'voltage(V)' and ylabel as 'sample(n)'
What code to do this?
I am so thanksful for help ^_^
Setting the x-axis with np.arange(0, 1, 0.001) gives an array from 0 to 1 in 0.001 increments.
x = np.arange(0, 1, 0.001) returns an array of 1000 points from 0 to 1, and y = np.sin(2*np.pi*x) you will get the sin wave from 0 to 1 sampled 1000 times
I hope this will help:
import matplotlib.pyplot as plt
import numpy as np
Fs = 8000
f = 5
sample = 8000
x = np.arange(sample)
y = np.sin(2 * np.pi * f * x / Fs)
plt.plot(x, y)
plt.xlabel('sample(n)')
plt.ylabel('voltage(V)')
plt.show()
P.S.: For comfortable work you can use The Jupyter Notebook.
import matplotlib.pyplot as plt # For ploting
import numpy as np # to work with numerical data efficiently
fs = 100 # sample rate
f = 2 # the frequency of the signal
x = np.arange(fs) # the points on the x axis for plotting
# compute the value (amplitude) of the sin wave at the for each sample
y = np.sin(2*np.pi*f * (x/fs))
#this instruction can only be used with IPython Notbook.
% matplotlib inline
# showing the exact location of the smaples
plt.stem(x,y, 'r', )
plt.plot(x,y)
import numpy as np
import matplotlib.pyplot as plt
F = 5.e2 # No. of cycles per second, F = 500 Hz
T = 2.e-3 # Time period, T = 2 ms
Fs = 50.e3 # No. of samples per second, Fs = 50 kHz
Ts = 1./Fs # Sampling interval, Ts = 20 us
N = int(T/Ts) # No. of samples for 2 ms, N = 100
t = np.linspace(0, T, N)
signal = np.sin(2*np.pi*F*t)
plt.plot(t, signal)
plt.xlabel('Time (s)')
plt.ylabel('Voltage (V)')
plt.show()
import math
import turtle
ws = turtle.Screen()
ws.bgcolor("lightblue")
fred = turtle.Turtle()
for angle in range(360):
y = math.sin(math.radians(angle))
fred.goto(angle, y * 80)
ws.exitonclick()
The window of usefulness has likely come and gone, but I was working at a similar problem. Here is my attempt at plotting sine using the turtle module.
from turtle import *
from math import *
#init turtle
T=Turtle()
#sample size
T.screen.setworldcoordinates(-1,-1,1,1)
#speed up the turtle
T.speed(-1)
#range of hundredths from -1 to 1
xcoords=map(lambda x: x/100.0,xrange(-100,101))
#setup the origin
T.pu();T.goto(-1,0);T.pd()
#move turtle
for x in xcoords:
T.goto(x,sin(xcoords.index(x)))
A simple way to plot sine wave in python using matplotlib.
import numpy as np
import matplotlib.pyplot as plt
x=np.arange(0,3*np.pi,0.1)
y=np.sin(x)
plt.plot(x,y)
plt.title("SINE WAVE")
plt.show()
import matplotlib.pyplot as plt
import numpy as np
#%matplotlib inline
x=list(range(10))
def fun(k):
return np.sin(k)
y=list(map(fun,x))
plt.plot(x,y,'-.')
#print(x)
#print(y)
plt.show()
This is another option
#!/usr/bin/env python
import numpy as np
import matplotlib
matplotlib.use('TKAgg') #use matplotlib backend TkAgg (optional)
import matplotlib.pyplot as plt
sample_rate = 200 # sampling frequency in Hz (atleast 2 times f)
t = np.linspace(0,5,sample_rate) #time axis
f = 100 #Signal frequency in Hz
sig = np.sin(2*np.pi*f*(t/sample_rate))
plt.plot(t,sig)
plt.xlabel("Time")
plt.ylabel("Amplitude")
plt.tight_layout()
plt.show()
Yet another way to plot the sine wave.
import numpy as np
import matplotlib
matplotlib.use('TKAgg') #use matplotlib backend TKAgg (optional)
import matplotlib.pyplot as plt
t = np.linspace(0.0, 5.0, 50000) # time axis
sig = np.sin(t)
plt.plot(t,sig)
from math import *
Fs = 8000
f = 500
sample = 16
a = [0] * sample
for n in range(sample):
a[n] = sin(2*pi*f*n/Fs)
creating the x coordinates
Sample = [i for i in range(sample)]
importing matplotlib for plotting
import matplotlib.pyplot as plt
adding labels and plotting
plt.xlabel('Voltage(V)')
plt.ylabel('Sample(n)')
plt.plot(Sample, a)
plt.show()