How to insert values in a zeros matrix?
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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 Comments
the cyclist
on 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)?
Answers (1)
Voss
on 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
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 Comments
Voss
on 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
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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