I'm getting an error which I don't understand: index exceeds matrix dimensions, what does it mean?

When i'm using this code: for i=1:size(m,1) VaR(i,1)=-quantile(AEurostoxAR(i+m,1),0.05); end

i'm getting this error: ??? Index exceeds matrix dimensions.

Does somebody know what the error means or what I am doing wrong in my code? I want to calculate the VaR with the historical simulation method. The AEurostoxAR are returns from the EuroStoxx 50 with 782 returns and i'm using a rolling window of 250, so my m=250

Thanks in advance,

kind regards Michiel

[Geoff Hayes]

Hi Michiel,

The error "Index exceeds matrix dimensions" usually means that the code is trying to access an element in a matrix using an index that is outside the dimension of the matrix:

x=zeros(5,1);  % vector with five elements
x(6)           % trying to access the sixth element which does not exist

It looks like there are only two places in your code where you are trying to access an element within a vector or matrix: either VaR or AEurostoxAR .

What are the dimensions of VaR ? Is it a vector (or matrix) with 250 rows (since m==250) and one column (250x1)? The dimensions of VaR may not matter so much since typically the matrix will grow at each iteration of the loop (may see a warning in the code alluding to this) if it has not been pre-sized.

Is m a scalar or a vector? You mention in you question that m=250 , but then in the for loop you iterate from 1 to size(m,1) . Are you expecting m to be a vector then and you are getting the number of its rows? If m is a vector, then what do you expect will happen when you do AEurostoxAR(i+m,1)?

What are the dimensions of AEurostoxAR?

Geoff

[Prasad Gianluca Colombage Fernando]

Hi I am from Italy and I have to doing a project between mimics and matlab; I have to read the mask created in mimics in matlab. When I do this this mistake occurs : Index exceeds matrix dimensions.

Error in femurmask (line 11) Houns=femur2(:,4)+754; How can I resolve it ?

[Bob Thompson]

@ Prasad,

What does the rest of your code look like? What are the dimensions of Houns and femur2? I suspect that 'femur2(:,4)+754' is not the problem, because this will just add 754 to each element of femur2. However, if Houns is not the same size as femur2, then you would get an 'Index exceeds matrix dimensions' error. Double check these two are the same size.

[Huda Zulfiqar]

Index exceeds matrix dimensions.

Error in Green (line 10)

a_g = a( :, :, 2 );

When i run the below code it shows the error "index exceeds matrix dimensions"

can anyone plzz help me to correct my code??

clc;

clear;

close;

% Read the image

a=imread('mouse.png');

% Convert to grayscale incase it is color

a = rgb2gray(a);

a_g = a( :, :, 2 );

b=size(a_g);

a=double(a_g);

% Loop for Getting the Histogram of the image

hist1 = zeros(1,256);

for i=1:b(1)

for j=1:b(2)

for k=0:255

if a(i,j)==k

hist1(k+1)=hist1(k+1)+1;

end

end

end

end

%Generating PDF out of histogram by diving by total no. of pixels

pdf=(1/(b(1)*b(2)))*hist1;

%Generating CDF out of PDF

cdf = zeros(1,256);

cdf(1)=pdf(1);

for i=2:256

cdf(i)=cdf(i-1)+pdf(i);

end

cdf = round(255*cdf);

ep = zeros(b);

for i=1:b(1) %loop tracing the rows of image

for j=1:b(2) %loop tracing thes columns of image

t=(a(i,j)+1); %pixel values in image

ep(i,j)=cdf(t); %Making the ouput image using cdf as the transformation function

end

end

% Loop for Getting the Histogram of the image

hist2 = zeros(1,256);

for i=1:b(1)

for j=1:b(2)

for k=0:255

if ep(i,j)==k

hist2(k+1)=hist2(k+1)+1;

end

end

end

end

subplot(2,2,1);

imshow(uint8(a_g));

title('Original Image');

subplot(2,2,2);

imshow(uint8(ep));

title('Image after Histogram Equalization');

subplot(2,2,3);

stem(hist1);

title('Histogram of the Original Image');

subplot(2,2,4);

stem(hist2);

title('Histogram after Histogram Equalization of the Original Image');

suptitle(' The original green channel image along with image after histogram equalization with their respective histograms')

[Stephen23]

a = rgb2gray(a); % the output of RGB2GRAY is MxNx1,
a_g = a( :, :, 2 ); % so what does this "2" refer to?

[Huda Zulfiqar]

splitting green channel

[Stephen23]

@Huda Zulfiqar: a 2D grayscale image does not have a green channel. You need to think about what your code is doing: you convert the image to grayscale (no green channel) and then try to access its green channel... how is that supposed to work?

Please stop spamming this forum with the same comment in multiple different threads.

[Huda Zulfiqar]

when i run the same code for red channel it works but when i try to split green or blue it dosen't work?

The below code is to split red channel

clc;

clear;

close;

% Read the image

a=imread('mouse.png');

% Convert to grayscale incase it is color

a = rgb2gray(a);

a_r = a( :, :, 1 );

b=size(a_r);

a=double(a_r);

% Loop for Getting the Histogram of the image

hist1 = zeros(1,256);

for i=1:b(1)

for j=1:b(2)

for k=0:255

if a(i,j)==k

hist1(k+1)=hist1(k+1)+1;

end

end

end

end

%Generating PDF out of histogram by diving by total no. of pixels

pdf=(1/(b(1)*b(2)))*hist1;

%Generating CDF out of PDF

cdf = zeros(1,256);

cdf(1)=pdf(1);

for i=2:256

cdf(i)=cdf(i-1)+pdf(i);

end

cdf = round(255*cdf);

ep = zeros(b);

for i=1:b(1) %loop tracing the rows of image

for j=1:b(2) %loop tracing thes columns of image

t=(a(i,j)+1); %pixel values in image

ep(i,j)=cdf(t); %Making the ouput image using cdf as the transformation function

end

end

% Loop for Getting the Histogram of the image

hist2 = zeros(1,256);

for i=1:b(1)

for j=1:b(2)

for k=0:255

if ep(i,j)==k

hist2(k+1)=hist2(k+1)+1;

end

end

end

end

subplot(2,2,1);

imshow(uint8(a_r));

title('Original Image');

subplot(2,2,2);

imshow(uint8(ep));

title('Image after Histogram Equalization');

subplot(2,2,3);

stem(hist1);

title('Histogram of the Original Image');

subplot(2,2,4);

stem(hist2);

title('Histogram after Histogram Equalization of the Original Image');

suptitle('The original red channel image along with image after histogram equalization with their respective histograms')

[Huda Zulfiqar]

@Stephen Cobeldick ok thanks alot sir

[Stephen23]

"when i run the same code for red channel it works but when i try to split green or blue it dosen't work?"

Nope, it does not "work" on the red channel (it actually "works" on a grayscale image).

"The below code is to split red channel"

No, it does not. Your code uses this line immediately after importing the image data:

a = rgb2gray(a);

to convert a (presumably) RGB image to an MxN grayscale matrix. After that line:

• a does not have a red channel.
• a does not have a green channel.
• a does not have a blue channel.

In the rest of your code a is a grayscale MxN matrix. An MxN matrix a does not have red, green or blue channels. It has no color infomation whatsoever, and certainly has no different color channels.

If you expect different color channels, why are you converting to grayscale?

[Huda Zulfiqar]

ohhh ok thanks a lot sir i was on mistake ...now i completely understand it