array "not used in this scope". Why? - c++

Question

I'm getting an error saying that "adjacencymatrix' was not used in this scope" right at the end of main (before the function makebond at the end) (the commented line 112 "BROKEN LINE"). Why? Sorry about this being simple. I'm compiling with g++ ($ g++ a.c -o f).
Heres the code:
#include <time.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
using namespace std;
#define PI 3.1415926535897932384626433832795
#define sqr(x) ((x)*(x))
#define count 500
double density;
double volume;
int N;
double beta = 0.1;
double R = 5;
double rob = 1;
int dimension = 2;
double eps=0.1; // Increase in density
double mindensity = 0; // Minimum density
double maxdensity = 8; // max.dens (scaled for the sake of ensuring int()
int makebond(double x);
int main(){
srand(time(0));
for (int rho=mindensity;rho<=(maxdensity/eps);density++){
N = floor(density*volume);
double nodepositions[N][dimension];
// Place nodes in volume (square side L, circle volume *R and obstacle *rob)
for (int i=0;i<N;i++){
int L = 5;
double distancefromorigin;
double x = (L*(rand()/RAND_MAX))-(L/2);
double y = (L*(rand()/RAND_MAX))-(L/2);
distancefromorigin = sqrt((x*x)+(y*y));
if(distancefromorigin<R){
if(distancefromorigin>rob){
nodepositions[i][0] = x;
nodepositions[i][1] = y;
}
}
}
double adjacencymatrix [N][N];
double itzhak; //distance of node 1 from the centre
double isaac; //distance of node 2 from the centre
double vivaldi; //distance between node 1 and node 2
double phi; // a function of the above 3 doubles (see later usage)
double rubicon; // maximum distance nodes within the icecream can be apart before becoming visually indepdendent
double maxtheta; // "in the icecream" means theta < maxtheta
double theta; // angular displacement of inner point from the line bisecting the icecream
// Create adjacency matrix (note alternative implementation using incidence lists)
for (int i=0;i<N;i++){
for (int j=0;j<N;j++){
double x0 = nodepositions[i][0];
double y0 = nodepositions[i][1];
double x1 = nodepositions[j][0];
double y1 = nodepositions[j][1];
itzhak = sqrt(sqr(x0) + sqr(y0));
isaac = sqrt(sqr(x1) + sqr(y1));
vivaldi = sqrt(sqr(x0-x1) + sqr(y0-y1));
phi = ((sqr(vivaldi)+sqr(itzhak)-sqr(isaac))/(2*vivaldi*itzhak));
rubicon = ((itzhak*phi) - sqrt((sqr(rob)) - ((sqr(itzhak))*(1-sqr(phi)))));
maxtheta = asin(rob/itzhak);
theta = acos(phi);
if (x0==x1 && y0==y1){
adjacencymatrix[i][j] = 0;
}
else{
if (isaac<itzhak && theta<maxtheta) {
if (vivaldi>rubicon){
adjacencymatrix[i][j] = 0;}
else {
adjacencymatrix[i][j] = makebond(vivaldi);}
}
else{adjacencymatrix[i][j] = makebond(vivaldi);}
}
}
}
}
FILE *datafc1;
datafc1 = fopen("matrix.dat", "w");
for (int ii = 0; ii<N; ii++){
for (int jj = 0; jj<N; jj++){
int aaa;
aaa = adjacencymatrix[ii][jj];///////////////*******BROKEN LINE******
fprintf(datafc1,"%i", aaa);
}
}
fclose(datafc1);
return 0;
}
/////////////////////////////
////////////////
/////// --End Main--
////////////////
////////////////////////////
int makebond(double x){
// This function takes in the euc. dist. between two nodes and draws a link with prob. H(r)
double randomnumber = (rand()/RAND_MAX); // Random number between 0 and 1
double hr = exp(-beta*sqr(x));// ***Connection function***
int a = 1; // Number to be put into adjacency matrix
if (randomnumber > hr){
a = 0;
}
return a; //Returns 0 or 1 depending on prob. dist.
}

Answer 1

adjacencymatrix is declared in your first for loop, so it's out of scope before the last spot you're using it, in the print-out loop at the bottom.
In addition, you have a useless using namespace std; line. Your code doesn't include any headers that contain std namespace symbols.

Answer 2

Your code in line 57:
double adjacencymatrix [N][N];
is inside a for loop, outside that loop, adjacencymatrix is undefined.

Answer 3

You matrix is defined in the for loop on line 11. Therefore it is out of scope on line 112.

Answer 4

FILE *datafc1;
datafc1 = fopen("matrix.dat", "w");
for (int ii = 0; ii<N; ii++){
for (int jj = 0; jj<N; jj++){
int aaa;
//error adjacencymatrix is declared in your first for loop
aaa = adjacencymatrix[ii][jj];///////////////*******BROKEN LINE******
fprintf(datafc1,"%i", aaa);
}
}