Array indices must be positive integers or logical values.

sigma = 1.0;

Red=double(Red);

NIR=double(NIR);

knr = exp(-(NIR-Red) ^2/(2*sigma ^2));

kNdvi = (1-knr)/(1+knr);

figure,imshow(kNdvi,[]);

colormap(summer);

colorbar;

Error in kNDVI (line 10)

knr = exp(-(NIR-Red) ^2/(2*sigma ^2));

Answer 1

[Image Analyst]

Try

Since NIR and Red are images, not scalar, try

knr = exp(-(NIR-Red) .^ 2 / (2*sigma ^2));

Note that I'm using .^ instead of ^.

[Simba]

Yes it finaly worked thank you.

Answer 2

[the cyclist]

Is it possible that you defined a variable called exp? If so, then MATLAB is trying to index into that variable, rather than calling the function. (Never name a variable the same as a MATLAB function.)

If that does not solve your problem, it would be helpful if you uploaded a MAT file and full code required to replicate the error. Otherwise, there is too much guesswork for us.

[Simba]

No I didnt declare exp but I am trying to use the function.

I am trying to formulate a code for this formula k(NIR, red ) = exp (  − ​(NIR − red)^2/ (2 σ^2) )

[the cyclist]

I won't be able to run your code locally, because I do not have the Image Processing Toolbox. But right now no one can run your code, because we don't have those input files. (It's difficult to tell if the inputs are important.)

[Simba]

thank you for the assistance.

Answer 3

[Image Analyst]

See the FAQ for a thorough discussion and explanation of the error:

https://matlab.fandom.com/wiki/FAQ#.22Subscript_indices_must_either_be_real_positive_integers_or_logicals..22