How to insert values in a zeros matrix?

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Aarti Soni
Aarti Soni il 16 Apr 2022
Commentato: Voss il 18 Apr 2022
Hello everyone,
I have created a zeros metrix X = 720x1440, the interval of each grid is 0.25. I have another matrix Y= 129x135, this matrix is having values. Now I want to insert the values of Y matrix into the X matrix.
The location of Y matrix is, 6.5:0.25:38.5 (129) and 66.5:0.25:100.0 (135)
Thank you
  3 Commenti
the cyclist
the cyclist il 16 Apr 2022
You told us the grid interval, but we also need to know the grid starting point. Does X(1,1) correspond to grid location (0,0)?
Aarti Soni
Aarti Soni il 16 Apr 2022
0.25:0.25:360;
-89.75:0.25:90;
1440x720 is a global grid and 129x135 is the location of India. The location of India is given in question.
I hope this is clear.

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Risposte (1)

Voss
Voss il 16 Apr 2022
all_lat = -89.75:0.25:90;
% according to the longitudes specified for India (66.5 to 100),
% longitude goes from -180 to 180, not 0 to 360:
all_lon = (0.25:0.25:360)-180;
india_lat = 6.5:0.25:38.5;
india_lon = 66.5:0.25:100.0;
whos *_lat *_lon
Name Size Bytes Class Attributes all_lat 1x720 5760 double all_lon 1x1440 11520 double india_lat 1x129 1032 double india_lon 1x135 1080 double
X = zeros(numel(all_lat),numel(all_lon)); % your zeros matrix
Y = rand(numel(india_lat),numel(india_lon)); % random matrix substituting for your Y matrix
% determine where Y belongs in X:
[~,idx_lat] = ismember(india_lat,all_lat);
[~,idx_lon] = ismember(india_lon,all_lon);
% set those elements of X to the values in Y:
X(idx_lat,idx_lon) = Y;
% plot to see the result
s = pcolor(all_lon,all_lat,X);
set(s,'EdgeColor','none');
  2 Commenti
Aarti Soni
Aarti Soni il 17 Apr 2022
@_ thanks for the code but I am getting values at this position.
Voss
Voss il 18 Apr 2022
One difference is that I used all_lon and all_lat as the x and y coordinates for my pcolor plot and you are using indices. Also, the 'YDir' of your axes is 'reverse'.
If I make those two changes I get your plot:
all_lat = -89.75:0.25:90;
% according to the longitudes specified for India (66.5 to 100),
% longitude goes from -180 to 180, not 0 to 360:
all_lon = (0.25:0.25:360)-180;
india_lat = 6.5:0.25:38.5;
india_lon = 66.5:0.25:100.0;
whos *_lat *_lon
Name Size Bytes Class Attributes all_lat 1x720 5760 double all_lon 1x1440 11520 double india_lat 1x129 1032 double india_lon 1x135 1080 double
X = zeros(numel(all_lat),numel(all_lon)); % your zeros matrix
Y = rand(numel(india_lat),numel(india_lon)); % random matrix substituting for your Y matrix
% determine where Y belongs in X:
[~,idx_lat] = ismember(india_lat,all_lat);
[~,idx_lon] = ismember(india_lon,all_lon);
% set those elements of X to the values in Y:
X(idx_lat,idx_lon) = Y;
% plot to see the result
% s = pcolor(all_lon,all_lat,X); % using all_lon and all_lat for x and y in pcolor
s = pcolor(X); % using 1:size(X,2), 1:size(X,1)
set(s,'EdgeColor','none');
set(gca(),'YDir','reverse'); % reverse the Y axis

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