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# Bilinear interpolation error - index exceeds matrix dimensions

Asked by P on 25 Jan 2013

I am supposed to do the bilinear interpolation without using imresize or interp. I am getting the error 'Index exceeds matrix dimensions' The padding was to avoid that.

fbilin(1:3:2769,1:3:2109)=f300(1:923,1:703);

for j=1:3:2109

```   for i=1:3:2769
f11=f300(i,j+2);
f12=f300(i,j+2);
f21=f300(i+2,j);
f22=f300(i+2,j+2);
fbilin(i+1,j+1)=(f11*((i+2)-(i+1))*((j+2)-(j+1))+...
f21*((i+1)-(i))*((j+2)-(j+1))+...
f12*((i+2)-(i+1))*((j+1)-(j))+...
f22*((i+1)-(i))*((j+1)-(j)))./((i+2)-(i))*((j+2)-(j));
end
end```

subplot(2,3,5), imagesc(fbilin), title('Chronometer Bilinear'); }

## 1 Comment

Image Analyst on 25 Jan 2013

Click edit (to the upper left). Put a blank line before your code. Then highlight all your code and click {}Code icon above to format your code properly.

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Answer by Matt J on 25 Jan 2013
Edited by Matt J on 25 Jan 2013

Use DBSTOP to halt execution at the point where the error occurs. Check the values of the indices at that point. Also check the size of the (supposedly padded) arrays.

P on 25 Jan 2013

i agree. I just cannot figure out how to run this loop to get the image.

Matt J on 25 Jan 2013

Well, one thing should be clear. If the size of the array is 931, you should probably not be running i up to 2769, and similarly for j. Where did these numbers come from anyway?

P on 26 Jan 2013

you are right. instead of f300 it should be fbilin. Thank you.