Help with nested for and if loops

I'm attempting to loop through my 140+ years of climate data to sift out wet and dry seasons in the tropics. I've written some code (below), but 'dry_clim' values aren't being printed. Does anyone see what I've missed here?

Thanks!

function dissect_seasons
%Break met driver into seasonal steps

%Load dataset
climatology=TropicalRainforest_evap;

%Set indices
Jan=(1:12:length(TropicalRainforest_evap));
Jan=Jan';
Feb=(2:12:length(TropicalRainforest_evap));
Feb=Feb';
Mar=(3:12:length(TropicalRainforest_evap));
Mar=Mar';
Apr=(4:12:length(TropicalRainforest_evap));
Apr=Apr';
May=(5:12:length(TropicalRainforest_evap));
May=May';
Jun=(6:12:length(TropicalRainforest_evap));
Jun=Jun';
Jul=(7:12:length(TropicalRainforest_evap));
Jul=Jul';
Aug=(8:12:length(TropicalRainforest_evap));
Aug=Aug';
Sep=(9:12:length(TropicalRainforest_evap));
Sep=Sep';
Oct=(10:12:length(TropicalRainforest_evap));
Oct=Oct';
Nov=(11:12:length(TropicalRainforest_evap));
Nov=Nov';
Dec=(12:12:length(TropicalRainforest_evap));
Dec=Dec';

%Manually set seasons for now, based on Koppen class rules & 100+ yr
%reanalysis climatologies
dryS=vertcat(Jun, Jul, Aug);
wetS=vertcat(Jan, Feb, Mar, Apr, May, Sep, Oct, Nov, Dec);
n=0
dry_clim=zeros(size(climatology));

   for j=1:length(TropicalRainforest_evap)

       for k=1:length(dryS)

       if climatology(:,:,j)==dryS(k)
           n=n+1;
           dry_clim(:, :, n)=climatology(:,:,j);
       end
       end
   end

[Sean de Wolski]

Any chance you could attach the data?

[Kate]

The files are pretty large, Tropical Rainforest_evap is a 2 degree grid evaporative fraction only for tropical rainforests on the globe: >> whos TropicalRainforest_evap Name Size Bytes Class Attributes

TropicalRainforest_evap      90x180x1692            109641600  single

[Kate]

wetS/dryS is essentially a vector of months which I want to pull out:

>> wetS

wetS =

           1
          13
          25
          37
          49
          61
          73
          85
          97
         109
         121
         133
         145
         157
         169
         181
         193
         205
         217
         229
         241
         253
         265
         277

[Kate]

I think that the issue is that I want to pull where climatology(:,:,k)=anything in dryS, does that make sense?

[Vivek Selvam]

climatology(:,:,j) would result in a 2 dimensional matrix and dryS(k) a scalar. That is why the comparison is always false and n=0 at the end. Correct me if I am wrong - you want to see if the scalar, dryS(k), matches with any element of climatology(:,:,j)?

Answer 1

[Vivek Selvam]

Changing the following line from

if climatology(:,:,j)==dryS(k)

to

if nnz(climatology(:,:,j)==dryS(k)) > 0

should make it work.

[Kate]

Unfortunately Matlab still doesn't find values and write them to the new matrix

[Vivek Selvam]

Hi Kate,

I think I understand what you need. I have modified your code.

%Manually set seasons for now, based on Koppen class rules & 100+ yr
%reanalysis climatologies
dryS     = vertcat(Jun, Jul, Aug);
wetS     = vertcat(Jan, Feb, Mar, Apr, May, Sep, Oct, Nov, Dec);
%%data extraction
dry_clim = climatology(:,:,dryS);
n        = length(dry_clim)

Hope this helped!