What does Undefined operator '-' for input arguments of type 'string' mean?

Hi, I am a beginner user of Matlab. I keep getting " Undefined operator '-' for input arguments of type 'string'", and I have no idea how I need to fix my script. Appreciate any help resolving this issue.

Below is my script:

%NDVI = (infrared - red)./(infrared + red);

NDVIs= ("subplots(299,:)"-"subplots(195,;)")./("subplots(299,:)"+"subplots(195,:)");

Error message:

Undefined operator '-' for input arguments of type 'string'.

Error in Exercise_NDVI (line 2)

NDVIs= ("subplots(299,:)"-"subplots(195,;)")./("subplots(299,:)"+"subplots(195,:)");

[Ameer Hamza]

What do you think that the line

NDVIs= ("subplots(299,:)"-"subplots(195,;)")./("subplots(299,:)"+"subplots(195,:)");

is supposed to do???

Answer 1

[Stephen23]

NDVIs = (subplots(299,:)-subplots(195,:))./(subplots(299,:)+subplots(195,:));

[Chinatsu Endo]

Thanks, Stephen. I use the exact script that you shared, and it worked (no more error!)