Set initial values for solving nonlinear equation by SAS proc IML - sas

I am using SAS proc IML to solve the nonlinear equation (x-0.11)(x-0.32)(x-0.98) = 0. I have to provide initial values for the proc IML. I would like to use 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 as initial values. The SAS program for initial value 0.1 is below. Now I have to repeat the SAS program below for each of the initial values. I am wondering if there is an elegant way to do it.
proc iml;
start Fun(var);
x = var[1];
f = j(1, 1, .); /* return a ROW VECTOR */
f[1] = (x-0.11)*(x-0.32)*(x-0.98);
return (f);
finish;
/* x constraints. Lower bounds in 1st row; upper bounds in 2nd row */
con = {1e-6, /* x > 0*/
. };
x0 = {0.1}; /* initial guess */
optn = {1 /* solve least square problem that has 1 components */
1}; /* amount of printing */
call nlphqn(rc, Soln, "Fun", x0, optn) blc=con; /* or use NLPLM */
print Soln;
create root var {Soln}; /** create data set **/
append; /** write data in vectors **/
close root; /** close the data set **/
quit;

I don't know anything about the kind of nonlinear solving you're doing, but at minimum you can loop it:
proc iml;
start Fun(var);
x = var[1];
f = j(1, 1, .); /* return a ROW VECTOR */
f[1] = (x-0.11)*(x-0.32)*(x-0.98);
return (f);
finish;
/* x constraints. Lower bounds in 1st row; upper bounds in 2nd row */
con = {1e-6, /* x > 0*/
. };
x0 = {0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0}; /* initial guesses */
optn = {1 /* solve least square problem that has 1 components */
1}; /* amount of printing */
create root var {Soln}; /** create data set **/
do i = 1 to 10;
call nlphqn(rc, Soln, "Fun", x0[i], optn) blc=con; /* or use NLPLM */
print Soln;
append; /** write data in vectors **/
end;
close root; /** close the data set **/
quit;
You might be able to pass the whole vector and do it more optimally that way, but not to the call nlphqn as you have it at least. You'd probably have to rewrite the function at least to accept the vector, and I'm not sure what that would do at that point - it may or may not work with nlphqn, I'm not sure.

Related

working with matrices and samples using PROC IML

I am trying to draw random samples from some distribution as follows:
my code runs but the numbers look strange. so I am not sure what went wrong, maybe some operators. The elements are extremely large.
my attempt:
C_hat=(((x`)*x)**(-1))*((x`)*z);
S=((z-x*c_hat)`)*((z-x*c_hat));
*draw sigma;
sigma = shape(RandWishart(1, 513 - 3 - 2,s**(-1)),4,4);
*draw vec(c);
vec_c_hat= colvec(c_hat`); *vectorization of c_hat;
call randseed(4321);
vec_c = RandNormal(1,vec_c_hat,(sigma`)#(((x`)*x)**(-1)));
c = shape(vec_c,4,4);
print c;
Since you haven't provided data or a reference, it is difficult to guess whether your "strange" and "extremely large" numbers are correct. However, the program looks mostly correct, so check your data.
A minor problem with your program is that you are using the SHAPE function to reshape the vec_c vector into a matrix. You should be using the SHAPECOL function (or transpose the result).
The following program uses the Sashelp.Cars data, which is distributed with SAS, to initialize the X and Z matrices. The program computes a random matrix C which is close to the inverse crossproduct matrix for the data. I've also added some intermediate computations and comments. This version works as expected on the Sashelp.Cars data:
proc iml;
use sashelp.cars;
read all var {weight wheelbase enginesize horsepower} into X;
read all var {mpg_city mpg_highway} into Z;
close;
*normal equations and covariance;
xpx = x`*x;
invxpx = inv(xpx);
C_hat = invxpx*(x`*z);
r = z-x*c_hat;
S = r`*r;
*draw sigma;
call randseed(4321);
DF = nrow(X)-ncol(X)-2;
W = RandWishart(1, DF, inv(S)); /* 1 x (p*p) row vector */
sigma = shape(W, sqrt(ncol(W))); /* reshape to p x p matrix */
*draw vec(c);
vec_c_hat = colvec(c_hat`); /* stack columns of c_hat */
vec_c = RandNormal(1, vec_c_hat, sigma#invxpx);
c = shapecol(vec_c, nrow(C_hat), ncol(C_hat)); /* reshape w/ SHAPECOL */
print C_hat, c;

SaS Scenario Generation

Can someone please help with the scenario below? I am very new to SaS and am not sure how to get this to work?
Simulate 200 observations from the following linear model:
Y = alpha + beta1 * X1 + beta2 * X2 + noise
where:
• alpha=1, beta1=2, beta2=-1.5
• X1 ~ N(1, 4), X2 ~ N(3,1), noise ~ N(0,1)
I have tried this code but not sure its completely accurate:
DATA ONE;
alpha = 1;
beta1 = 2;
beta2 = -1.5;
RUN;
DATA CALC;
SET ONE;
DO i = 1 to 200;
Y=alpha+beta1*X1+beta2*X2+Noise;
X1=Rannor(1);
X2=rannor(3);
Noise=ranuni(0);
OUTPUT;
END;
RUN;
PROC PRINT DATA=CALC;
RUN;
You need to have a look in the SAS help for the topics
"rannor","ranuni","generating random numbers",...
rannor: generating standard normal distributed RVs.
ranuni: uniform distributed RVs.
The argument in rannor is the seed number, not the expected value.
If N(x,y) in your example means that the random variable is normally distributed with expected value x and standard deviation y (or do you mean the variance???) then the code could be (have a look on the changed order of the statements; the definition of Y has to be after the definition of the random numbers...):
DATA ONE;
alpha = 1;
beta1 = 2;
beta2 = -1.5;
RUN;
DATA CALC;
SET ONE;
seed = 1234;
DO i = 1 to 200;
X1=1+4*Rannor(seed);
X2=3+rannor(seed);
Noise=rannor(seed);
Y=alpha+beta1*X1+beta2*X2+Noise;
OUTPUT;
END;
RUN;
PROC PRINT DATA=CALC;
RUN;
There are also variants for generating random numbers, e.g. "call rannor". There are different concepts to deal with seed numbers in SAS. See the SAS help for these topics, e.g. here

IML correlation from different matrices

given a matrix X(n * p), I want to split X into Y1(n * p-k) and Y2(n * k), where Y1 is composed by the first k columns of X and Y2 the others.
Now, in R I can get the "crossed" correlation between the columns of Y1 and Y2 calling cor(Y1,Y2, use="pairwise.complete.obs"), how can I get the same result in SAS IML where the corr function admits only 1 dataset?
I tried to find an appropriate solution or algorithm to implement it but with bad results.
Can anyone help with this? Also pointing me some literature about this kind or correlation would be great! I don't want you to code it for me, simply some help or hint on existing functions or algorithms to translate.
Thank you.
EDIT: don't search on the web for crossed correlation, I wrote it simply for trying to explain myself.
Looking up "crossed correlation" leads you to a series of literature on signal processing and a function much like the autocorrelation function. In fact, in R it is documented with acf https://stat.ethz.ch/R-manual/R-devel/library/stats/html/acf.html.
But that is not what your code is doing. In R:
n = 100
p = 6
k = 2
set.seed(1)
r = rnorm(n*p)
x= matrix(r,n,p)
y1 = x[,1:k]
y2 = x[,(k+1):p]
cor.ys = cor(y1,y2,use="pairwise.complete.obs")
cor.x = cor(x)
(cor.ys - cor.x[1:k,(k+1):p])
You see the result from cor(y1,y2) is just a piece of the correlation matrix from x.
You should be able to put this in IML easily.
I can think of a few ways to do this. The simplest is to compute the full matrix of Pearson correlations (using the pairwise option) and then subset the result. (What DomPazz said.) If you have hundreds of variables and you only want a few of the correlations, it will be inefficient, but it is very simple to program:
proc iml;
n = 100; p = 6; k = 2;
call randseed(1);
x = randfun(n//p, "Normal");
varNames = "x1":"x6";
corr = corr(x, "pearson", "pairwise"); /* full matrix */
idx1 = 1:k; /* specify VAR */
idx2 = (k+1):p; /* specify WITH */
withCorr = corr[idx2, idx1]; /* extract submatrix */
print withcorr[r=(varNames[idx2]) c=(varNames[idx1])];
Outside of SAS/IML you can use PROC CORR and the WITH statement to do the same computation, thereby validating your SAS/IML program:
proc corr data=test noprob nosimple;
var x1-x2;
with x3-x6;
run;

How to do multiplication between two matrix using IML in SAS

I have data set named input_data below import from EXCEL.
0.353481635 0.704898683 0.078640917 0.813815803 0.510842666 0.240912872 0.986312218 0.781868961 0.682272971
0.443441526 0.653187181 0.753981865 0.34909803 0.84215961 0.793863082 0.047816942 0.176759112 0.54213244
0.21443281 0.142501578 0.927011587 0.407251043 0.290280445 0.90730524 0.677030212 0.770541244 0.915728969
0.583493041 0.685127614 0.119042255 0.067769934 0.795793907 0.405029459 0.817724346 0.594170688 0.345660875
0.816193304 0.636823417 0.036348358 0.027985453 0.117027493 0.436516667 0.593191955 0.916981676 0.574223091
0.766842249 0.743249552 0.400052263 0.809650253 0.683610082 0.42152573 0.050520292 0.329441952 0.868549022
0.112847881 0.462579082 0.526220066 0.320851313 0.944585551 0.233027402 0.66141107 0.8380858 0.120044416
0.873949265 0.118525986 0.590234323 0.481974796 0.668976582 0.466558592 0.934633956 0.643438048 0.053508922
And I have another data set called p below
data p;
input p;
datalines;
0.12
0.23
0.11
0.49
0.52
0.78
0.8
0.03
0.02
run;
proc transpose data = p out=p2;
run;
What I want to do is matrix manipulation in IML using SAS.
I have some code already, but the final calculation got error. Can someone give me a hand?
proc iml;
use input_data;
read all var _num_ into x;
print x;
proc iml;
use p2;
read all var _num_ into k;
print k;
proc iml;
Value1 = k * x;
print Value1;
quit;
You have several problems here.
First off, you have three PROC IML statements. PROC IML only persists values while it's running; once it quits, all of the vectors go away forever. So remove the PROC IMLs.
Second, you need to make sure your matrices are correctly ordered and structured. Matrix multiplication works by the following:
m x n * n x p = m x p
Where both N's must be the same. This is rows x columns, so the left-side matrix must have the same number of columns as the right-side matrix has rows. (This is because each element of each row on the left-side matrix is multiplied by the corresponding element in the column on the right-side matrix and then summed, so if the numbers don't match it's not possible to do.)
So you have 8x9 and 9x1, which you transpose to 1x9. So first off, don't transpose p, leave it 9x1. Then, make sure you have the order right (matrix multiplication is NOT commutative, the order matters). k * x means 9x1 * 8x9 which doesn't work (since 1 and 8 aren't the same - remember, the inner two numbers have to match.) x*k does work, since that is 8x9 * 9x1, the two 9s match.
Final output:
proc iml;
use input_data;
read all var _num_ into x;
print x;
use p;
read all var _num_ into k;
print k;
Value1 = x * k;
print Value1;
quit;

Compute percentages in a PROC REPORT

PRODUCT CODE Quantity
A 1 100
A 2 150
A 3 50
total product A 300
B 1 10
B 2 15
B 3 5
total product B 30
I made a proc report and the break after product gives me the total quantity for each product. How can I compute an extra column on the right to calculate the percent quantity of product based on the subtotal?
SAS has a good example of this in their documentation, here. I reproduce a portion of this with some additional comments below. See the link for the initial datasets and formats (or create basic ones yourself).
proc report data=test nowd split="~" style(header)=[vjust=b];
format question $myques. answer myyn.;
column question answer,(n pct cum) all;
/* Since n/pct/cum are nested under answer, they are columns 2,3,4 and 5,6,7 */
/* and must be referred to as _c2_ _c3_ etc. rather than by name */
/* in the OP example this may not be the case, if you have no across nesting */
define question / group "Question";
define answer / across "Answer";
define pct / computed "Column~Percent" f=percent8.2;
define cum / computed "Cumulative~Column~Percent" f=percent8.2;
define all / computed "Total number~of answers";
/* Sum total number of ANSWER=0 and ANSWER=1 */
/* Here, _c2_ refers to the 2nd column; den0 and den1 store the sums for those. */
/* compute before would be compute before <variable> if there is a variable to group by */
compute before;
den0 = _c2_;
den1 = _c5_;
endcomp;
/* Calculate percentage */
/* Here you divide the value by its denominator from before */
compute pct;
_c3_ = _c2_ / den0;
_c6_ = _c5_ / den1;
endcomp;
/* This produces a summary total */
compute all;
all = _c2_ + _c5_;
/* Calculate cumulative percent */
temp0 + _c3_;
_c4_ = temp0;
temp1 + _c6_;
_c7_ = temp1;
endcomp;
run;