Unable to perform assignment because the left and right sides have a different number of elements.

I would like to use code of SOR method. Here is the code:

% SOR ALGORITHM 7.3
%
% To solve Ax = b given the parameter w and an initial approximation
% x(0):
%
% INPUT:   the number of equations and unknowns n; the entries
%          A(I,J), 1<=I, J<=n, of the matrix A; the entries
%          B(I), 1<=I<=n, of the inhomogeneous term b; the
%          entries XO(I), 1<=I<=n, of x(0); tolerance TOL;
%          maximum number of iterations N; parameter w (omega).
%
% OUTPUT:  the approximate solution X(1),...,X(n) or a message
%          that the number of iterations was exceeded.
 syms('OK', 'AA', 'NAME', 'INP', 'N', 'I', 'J', 'A', 'X1');
 syms('TOL', 'NN', 'W', 'K', 'ERR', 'S', 'FLAG', 'OUP');
 TRUE = 1;
 FALSE = 0;
 fprintf(1,'This is the SOR Method for Linear Systems.\n');
 OK = FALSE;
 fprintf(1,'The array will be input from a text file in the order:\n');
 fprintf(1,'A(1,1), A(1,2), ..., A(1,n+1) \n');
 fprintf(1,'A(2,1), A(2,2), ..., A(2,n+1),\n');
 fprintf(1,'..., A(n,1), A(n,2), ..., A(n,n+1)\n\n');
 fprintf(1,'Place as many entries as desired on each line, but \n');
 fprintf(1,'separate entries with at least one blank.\n');
 fprintf(1,'The initial approximation should follow in same format.\n\n\n');
 fprintf(1,'Has the input file been created? - enter Y or N.\n');
 AA = input(' ','s');
 if AA == 'Y' | AA == 'y' 
 fprintf(1,'Input the file name in the form - drive:\\name.ext\n');
 fprintf(1,'for example:   A:\\DATA.DTA\n');
 NAME = input(' ','s');
 INP = fopen(NAME,'rt');
 OK = FALSE;
 while OK == FALSE 
 fprintf(1,'Input the number of equations - an integer.\n');
 N = input(' ');
 if N > 0 
 A = zeros(N,N+1);
 X1 = zeros(1,N);
 for I = 1 : N 
 for J = 1 : N+1 
 A(I,J) = fscanf(INP, '%f',1);
 end;
 end;
 for I = 1 : N 
 X1(I) = fscanf(INP, '%f',1);
 end;
% use X1 for X0
 OK = TRUE;
 fclose(INP);
 else
 fprintf(1,'The number must be a positive integer.\n');
 end;
 end;
 OK = FALSE;
 while OK == FALSE 
 fprintf(1,'Input the tolerance.\n');
 TOL = input(' ');
 if TOL > 0 
 OK = TRUE;
 else
 fprintf(1,'Tolerance must be a positive number.\n');
 end;
 end;
 OK = FALSE;
 while OK == FALSE 
 fprintf(1,'Input maximum number of iterations.\n');
 NN = input(' ');
 if NN > 0 
 OK = TRUE;
 else
 fprintf(1,'Number must be a positive integer.\n');
 end;
 end;
 fprintf(1,'Input parameter w (omega)\n');
 W = input(' ');
% use W for omega
 else
 fprintf(1,'The program will end so the input file can be created.\n');
 end;
 if OK == TRUE 
% STEP 1
 K = 1;
 OK = FALSE;
% STEP 2
 while OK == FALSE & K <= NN 
% ERR is used to test accuracy - it measures the infinity norm
 ERR = 0;
% STEP 3
 for I = 1 : N 
 S = 0;
 for J = 1 : N 
 S = S-A(I,J)*X1(J);
 end;
 S = W*(S+A(I,N+1))/A(I,I);
 if abs(S) > ERR 
 ERR = abs(S);
 end;
 X1(I) = X1(I)+S;
 end;
% STEP 4
 if ERR <= TOL  
 OK = TRUE;
% process is complete
 else
% STEP 5
 K = K+1;
% STEP 6 - is not used since only one vector is required
 end;
 end;
 if OK == FALSE 
 fprintf(1,'Maximum Number of Iterations Exceeded.\n');
% STEP 7
% procedure completed unsuccessfully
 else
 fprintf(1,'Choice of output method:\n');
 fprintf(1,'1. Output to screen\n');
 fprintf(1,'2. Output to text file\n');
 fprintf(1,'Please enter 1 or 2.\n');
 FLAG = input(' ');
 if FLAG == 2 
 fprintf(1,'Input the file name in the form - drive:\\name.ext\n');
 fprintf(1,'for example:   A:\\OUTPUT.DTA\n');
 NAME = input(' ','s');
 OUP = fopen(NAME,'wt');
 else
 OUP = 1;
 end;
 fprintf(OUP, 'SOR ITERATIVE METHOD FOR LINEAR SYSTEMS\n\n');
 fprintf(OUP, 'The solution vector is :\n');
 for I = 1 : N 
 fprintf(OUP, ' %11.8f', X1(I));
 end;
 fprintf(OUP, '\nusing %d iterations with\n', K);
 fprintf(OUP, 'Tolerance  %.10e in infinity-norm\n', TOL);
 fprintf(OUP, 'with Parameter %.10e\n', W);
 if OUP ~= 1 
 fclose(OUP);
 fprintf(1,'Output file %s created successfully \n',NAME);
 end;
 end;
 end;

And my data matrix is:

 1   -0.5   0   0   0   0   0
-0.5   1   -0.5   0   0   0   0
0   -0.5   1   -0.5   0   0   0
0   0   -0.5   1   -0.5   0   0
0   0   0   -0.5   1   -0.5   0   
0   0   0   0   -0.5   1   -0.5
0   0   0   0   0   -0.5   1

But I got error like this:

Has the input file been created? - enter Y or N.
 Y
Input the file name in the form - drive:\name.ext
for example:   A:\DATA.DTA
 ALG073.DTA
Input the number of equations - an integer.
 7
Unable to perform assignment because the left and right sides have a different number of elements.

Error in ALG073 (line 47)
 X1(I) = fscanf(INP, '%f',1);
 

Can anyone help?

Answer 1

[Walter Roberson]

When you enter 7 then the code expects to read 7 lines with 8 values per line (though as the prompts hint you can put as many values per line as you want, but the order will be groups of 8 values go into each row)

After that the file needs 7 numeric initial values.

The data matrix you posted is only 7x7 not 7x8. If your file then what you intend as 7 initial values they would be read in as the rest of the A values. Then when the code went to read the initial values it would not find any.