How to obtain and locate group of pixel value from .mat file

Hi Folks,

I have extracted chlorophyll from nc file attached

https://drive.google.com/file/d/1wLVlyQCorT2iDWb4NMPeWsU2NTuX-D-C/view?usp=sharing

chlor_a max value 93.9236, chlor_a min value 0.0373

To identify and locate the number of pixels and its values which falls in particular grid

For example - I need to classify with pixel value interval with respective Lat [0 30] , Lon[30 100] (row and column) as shown and save in .csv/ .xls

range

0 - 2

2 - 4

4 - 6

6 - 8

8 - 10

10 - to the max

Thanks in advance

Kindly help

regards

Answer 1

[KSSV]

Read about logical indexing. Let C be your data.

idx = C >= 0 & C < 2 ; 
c02 = C(idx) ; 
idx = C >= 2 & C < 4 ; 
c24 = C(idx) ; 

Also with the same indices you can get respective lon and lat.

[Karthik M]

Hi @KSSV

Thank you for the response

Whlile indexing I got one column of pixel values

I used this code to find the coordinates with pixel values at certain points but couldn't succeed

[maxval,maxind]=max(data(:));

[r,c]=ind2sub(size(data),maxind);

kindly help

[KSSV]

You need not to use ind2sub. Straight away use maxind.

[Karthik M]

Hi @KSSV

Thanks in advance

I could get the indexed position of the rows and columns of max / index value data with the below code

maxval=max(data(:));

[xmax,ymax]=find(data==maxval);

[ii,jj]=find(data >= 0 & data < 2);

but I need only the exact x and y location coordinates

I have classify the the pixel range according to my requirement as below

idx = data >= 0 & data< 2 ;

pix1 = data(idx);

idx = data >= 2 & data < 4 ;

pix2 = data(idx) ;

idx = iwant >= 4 & iwant < 6 ;

pix3 = data(idx) ;

idx = data >= 6 & data < 8 ;

pix4 = data(idx) ;

idx = data >= 8 & data < 10;

pix5 = data(idx);

idx = data >= 10 & data < 15 ;

pix6 = data(idx) ;

idx = data >= 15 & data < 20 ;

pix7 = data(idx) ;

idx= data >= 20 & data < 95;

pix8 = data(idx);

Kindly help to get the exact x, y position of the group data