Unequal left and right sides of matrix

% get parameters, allocate memory (I'm not having issues with this)
tiledimensions = 5000

tiledimensions = 5000

cornerUlLat = 39.2369

cornerUlLat = 39.2369

tiledimensions = 5000;
cornerUlLat = 39.2369;
nextlatpixel_1310 = 39.2366153;
tile1310_lat = zeros(5000);
delta_lat = 0.0002847;
% make matrix (here is where I'm confused)
tile1310_lat(:,1) = [cornerUlLat; nextlatpixel_1310];

Unable to perform assignment because the size of the left side is 5000-by-1 and the size of the right side is 2-by-1.

for i = 2:tiledimensions
       tile1310_lat(:,i) = tile1310_lat(:,i-1) - delta_lat;
end 
tile1310_lat;

I'm trying to make a 5000x5000 matrix of latitude values. The final product I want is for the latitudes to change going down the same column, but be the same across the same row. For example, this would look like:

39, 39, 39...

38, 38, 38....

I know what my delta needs to be and I think the for loop I have now would make the latitude values changing going down the column, but I want to copy each column across to the 5000th column so that I can have a latitude value for each pixel. I want to do the same thing for longitude later, but with the rows changing by delta_long and the columns staying the same (since longitude is x).

longitude:

104, 103, 102...

104, 103, 102...

My veryyyyy end goal is to have three matricies that are all 5000 by 5000: one for latitude, one for longitude, and one for my Landsat image data, then combine them into one matrix.

How would I copy each respective value list across and fix this error?

Answer 1

[dpb]

Going at it hard way...use MATLAB vector operations --

M=cornerUlLat-[0:tiledimensions-1].'*delta_lat;     % create first vector
M=repmat(M,1,tiledimensions);                       % and duplicate it

Gives you

>> whos M
Name         Size                  Bytes  Class     Attributes
  M         5000x5000            200000000  double              
>> M(1:5,1:10)

ans =

   39.2369   39.2369   39.2369   39.2369   39.2369   39.2369   39.2369   39.2369   39.2369   39.2369
   39.2366   39.2366   39.2366   39.2366   39.2366   39.2366   39.2366   39.2366   39.2366   39.2366
   39.2363   39.2363   39.2363   39.2363   39.2363   39.2363   39.2363   39.2363   39.2363   39.2363
   39.2360   39.2360   39.2360   39.2360   39.2360   39.2360   39.2360   39.2360   39.2360   39.2360
   39.2358   39.2358   39.2358   39.2358   39.2358   39.2358   39.2358   39.2358   39.2358   39.2358

>> 

[Eric Williams]

Yes! That worked! This method is for sure some big boy code, which I'm not super familiar with. I am now working on getting my longotude matrix, which is the same dimensions as this, except the values change by row rather than going down the column.

longitude:

104, 103, 102...

104, 103, 102...

Do you know how I could make this? I see that you used the apostrophe to transpore. I removed the apostrophe in hopes that it would work, but I got a 2x5000 matrix that changes down the column rather than left to right across the rows.

Thank you and here's what I have so far:

M2=cornerUlLon-[0;tiledimensions-1].*delta_long;     % create first vector
M2=repmat(M2,1,tiledimensions);       % and duplicate it
% try a comma instead of a semicolon or some other punctuation that will
% make it change by row????? 

[dpb]

Think about what you're building -- the first case needed to build a column vector to replicate; look at what the colon operator builds...

>> M=[0:tiledimensions-1];
>> whos M
  Name      Size              Bytes  Class     Attributes

  M         1x5000            40000  double              

>> format short, format compact
>> M(1:10)
ans =
     0     1     2     3     4     5     6     7     8     9
>> 

and you see colon (:) build a row vector -- so, we must transpose it to replicate it horizontally for the duplicates.

Now you want to duplicate a row vector going down -- so, the first idea is correct, don't transpose the original output; keep it as a row vector. But, whereas we made 1 copy vertically and tiledimension copies horizontally, now you need to do the reverse -- make the copies by row but only one copy wide --

M2=repmat(M2,tiledimensions,1);       % and duplicate it

It helps when playing with this stuff to use small toy-sized arrays of 10 or so elements max so that you can see the results conveniently in the command window while you work it out...