Matrix dimensions must agree error

I have the following code and couldn't figure out what I am doing wrong. I am getting the following error,

X0 = [0.001;0.001;0.001;0.001;0.001;0.001];
maxIter =100;
tolX = .01;
% Computation
X = X0;
Xold = X0;
 R = inv(j),
for i =1:maxIter
    [f,j]=new(X);   
    X = (X-R*f);
    err(:,i) = (X-Xold)
    Xold = X;
  X =[0 pi/2; 0 pi/2; 0 pi/2; 0 pi/2; 0 pi/2; 0 pi/2;];
    if  (err(:,i)<tolX)
        break;
    end
end

[Sindar]

please copy the full error (all red text) into your answer

[Avismit Dutta]

function [fval,jac]=new(X)

a = X(1);
b = X(2);
c = X(3);
d = X(4);
e = X(5);
f = X(6);
 
fval(1,1)=cosd(5*a)+cosd(5*b)+cosd(5*c)+cosd(5*d)+cosd(5*e)+cosd(5*f);
fval(2,1)=cosd(7*a)+cosd(7*b)+cosd(7*c)+cosd(7*d)+cosd(7*e)+cosd(7*f);
fval(3,1)=cosd(11*a)+cosd(11*b)+cosd(11*c)+cosd(11*d)+cosd(11*e)+cosd(11*f);
fval(4,1)=cosd(13*a)+cosd(13*b)+cosd(13*c)+cosd(13*d)+cosd(13*e)+cosd(13*f);
fval(5,1)=cosd(17*a)+cosd(17*b)+cosd(17*c)+cosd(17*d)+cosd(17*e)+cosd(17*f);
fval(6,1)=cosd(19*a)+cosd(19*b)+cosd(19*c)+cosd(19*d)+cosd(19*e)+cosd(19*f);

jac=  [-5*sind(5*X(1)),-5*sind(5*X(2)),-5*sind(5*X(3)),-5*sind(5*X(4)),-5*sind(5*X(5)),-5*sind(5*X(6));
     -7*sind(7*X(1)),-7*sind(7*X(2)),-7*sind(7*X(3)),-7*sind(7*X(4)),-7*sind(7*X(5)),-7*sind(7*X(6));
     -11*sind(11*X(1)),-11*sind(11*X(2)),-11*sind(11*X(3)),-11*sind(11*X(4)),-11*sind(11*X(5)),-11*sind(11*X(6));
     -13*sind(13*X(1)),-13*sind(13*X(2)),-13*sind(13*X(3)),-13*sind(13*X(4)),-13*sind(13*X(5)),-13*sind(13*X(6));
     -17*sind(17*X(1)),-17*sind(17*X(2)),-17*sind(17*X(3)),-17*sind(17*X(4)),-17*sind(17*X(5)),-17*sind(17*X(6));
     -19*sind(19*X(1)),-19*sind(19*X(2)),-19*sind(19*X(3)),-19*sind(19*X(4)),-19*sind(19*X(5)),-19*sind(19*X(6))];

[Avismit Dutta]

X0 = [0.001;0.001;0.001;0.001;0.001;0.001];
maxIter =100;
tolX = .01;
% Computation
X = X0;
Xold = X0;
 R = inv(j),
for i =1:maxIter
    [f,j]=new(X);   
    X = (X-R*f);
    err(:,i) = (X-Xold)
    Xold = X;
  X =[0 pi/2; 0 pi/2; 0 pi/2; 0 pi/2; 0 pi/2; 0 pi/2;];
    if  (err(:,i)<tolX)
        break;
    end
end

[Avismit Dutta]

this error is shown..

Error using  - 
Matrix dimensions must agree.

Error in ad (line 10)
    X = (X-R*f);
    

[Sindar]

So, if I'm reading this correctly, X should be 6x1, f should be 6x1, and R should be 6x6? So R*f should be 6x1. Check these sizes

Answer 1

[Guillaume]

The error message is very clear, R*f is not the same size as X (or a size compatible with X), hence you can't do the subtraction. Since we don't know what R or f is we can't tell what their size is.

Note that numbered or sequentially named variables are a bad idea. It forces you to complicate the code. For example, this whole lot:

a = X(1);
b = X(2);
c = X(3);
d = X(4);
e = X(5);
f = X(6); 
fval(1,1)=cosd(5*a)+cosd(5*b)+cosd(5*c)+cosd(5*d)+cosd(5*e)+cosd(5*f);
fval(2,1)=cosd(7*a)+cosd(7*b)+cosd(7*c)+cosd(7*d)+cosd(7*e)+cosd(7*f);
fval(3,1)=cosd(11*a)+cosd(11*b)+cosd(11*c)+cosd(11*d)+cosd(11*e)+cosd(11*f);
fval(4,1)=cosd(13*a)+cosd(13*b)+cosd(13*c)+cosd(13*d)+cosd(13*e)+cosd(13*f);
fval(5,1)=cosd(17*a)+cosd(17*b)+cosd(17*c)+cosd(17*d)+cosd(17*e)+cosd(17*f);
fval(6,1)=cosd(19*a)+cosd(19*b)+cosd(19*c)+cosd(19*d)+cosd(19*e)+cosd(19*f);

can be replaced with just:

%X is a column vector
fval = sum(cosd([5; 7; 11; 13; 17; 19] .* X.'), 2);

[Avismit Dutta]

this kind of error is shown

Error using  .* 
Matrix dimensions must agree.

Error in awa (line 1)
fval = sum(cosd([5; 7; 11; 13; 17; 19] .* X.'),
2);

[Walter Roberson]

Which MATLAB release are you using?

[Avismit Dutta]

matlab 2016

[Walter Roberson]

fval = sum(bsxfun(@times, cosd([5; 7; 11; 13; 17; 19], X.')),2);