MATLAB: Sub2ind problem

sub2ind

Hi, I have the following code.

    index1=sub2ind(size(I),r1,c1);
    info{i}(:,1)=I(index1);

It shows me the following error:

??? Subscripted assignment dimension mismatch.

can anybody help?

Best Answer

Please inspect the values of r1, index1 and i. Most likely "size(I(index1))" does not match the needed column vector size.

We do not have magic tools to solve this problem. Everything we can do to solve the problem, can be done by yourself also. But you have additional knowledge about the values of all variables.

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MATLAB: Sub2ind error

You need to convert from "real world units" into units of matrix elements. Below I used the "point-slope" formula for a line to convert your real world units into indexes. Here's one way that's fairly general for linear transforms like you used: (It's not that complicated, just try to follow the comments.)

mat=zeros(250,250);
% Create sample x and y vectors in "real world" units.
x=linspace(0,25.1923,100); % Columns
y=linspace(-7.9089e+003,313,100); % Rows.
% Figure out what indexes those are
% in terms of elements or indexes.
% These indexes will range from 1 to 100 (or the length of x or y).
slopeX = (max(x) - min(x)) / (length(x)-1)
rowIndexes = int32(1 + (x - min(x))/ slopeX)
slopeY= (max(y) - min(y)) / (length(y)-1)
columnIndexes = int32(1 + (y - min(y))/ slopeY)
% Now construct a list of all linear indices in the entire mat matrix.
% (That was wanted for some reason.)
linearIndexes = sub2ind(size(mat), rowIndexes, columnIndexes)
% Now do it for just one particular x and y 
% where x and y are in "real world" units.
x0 = 13  % Let's just say you wanted this for example.
y0 = 42
rowIndex = int32(1 + x0 / slopeX)
columnIndex = int32(1 + y0 / slopeX)
% Get the linear index of that one particular point.
linearIndex = sub2ind(size(mat),round(rowIndex),round(columnIndex))
% Report the value of mat() there:
fprintf('mat(%d) = %f\n', linearIndex, mat(linearIndex));

MATLAB: Subscripted assignment dimension mismatch.

The result of the find is likely a vector, and it appears you are trying to stuff this vector into a scalar spot. Do you need all of the find results, or maybe just one of them? If you need all of them, can you use a cell array for var? What is var being used for downstream in your code?

Best Answer

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MATLAB: Sub2ind error

MATLAB: Subscripted assignment dimension mismatch.

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