Accessing elements from 2d array using for loop

I am using MATLAB for image processing

I have made gradmag as an outline of brain MRI scan and fgm4 is only the tumor region of the MRI.

Both are 2d arrays.

The following code, however, gives error:

G1 = zeros(200,200);

for i=1:200

for j=1:200

if((gradmag[i][j]>0) && fgm4[i][j]>0)

G1[i][j]=255;

end

end

end

figure

imshow(G1); title("Outline");

The error:

Error: File: test1.m Line: 106 Column: 20

Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check

for mismatched delimiters.

Line 106 refers to the if statement

Answer 1

[Ameer Hamza]

In MATLAB parenthesis are used for indexing, So change your code lines to

if((gradmag(i,j)>0) && fgm4(i,j)>0)

and

G1(i,j)=255;

Also read here: https://www.mathworks.com/company/newsletters/articles/matrix-indexing-in-matlab.html

You can also take this course: https://www.mathworks.com/learn/tutorials/matlab-onramp.html to learn basics about MATLAB.

[Meenal Shah]

Thank you so much!!!

[Ameer Hamza]

I am glad to be of help.