MATLAB: For command in function

forfunctionMATLAB

I have a function attached and would like it to automatically run it with x = 2:4 & y = 2:4, that is, the function to run 8 times & have 8 outputs, with inputs

x =2, y = 2

x = 2, y = 3

x = 2, y = 4

x = 3, y = 2

…

Should I write a 'for' command with the function? It does not seem to work the best this way.

Best Answer

You can use pdist2()

[X,Y] = meshgrid(2:4);
x = X(:);
y = Y(:);
D = pdist2(rowsncolumns,[x y]);
% D(:,1) - first column of D - distance from (rowscolumns) to (x1,y1) point

Indices you want: D == 0

Size of D: 621 x 9

Related Solutions

MATLAB: Problem with an equation

Presumably you are not intending to perform matrix multiplication, but rather element-wise multiplication. Here are two methods to get use element-wise multiplication to get an output, even if the input vectors are different lengths:

x = -3:0.01:3;
y = -4:0.01:4;
% method 1: ndgrid
[X,Y] = ndgrid(x,y);
Z1 = cos(X.*Y).*(1+3*exp(X.^2+2*Y.^2));
% method 2: bsxfun
Z2 = cos(bsxfun(@times,x(:),y)) .* (1+3*exp(bsxfun(@plus,x(:).^2,2*y.^2)));

both of these give exactly the same result:

>> isequal(Z1,Z2)
ans =
     1
>> size(Z1)
ans =
   601   801

So the Z matrices have numel(x) rows and numel(y) columns. Thus you get an output value for each element in x and y.

Note that I reduced the number of points in the vectors (from 6001 and 8001 to 601 and 801), just to make it easier to work with.

I also removed the minus sign from after the exp fucntion as this is not MATLAB syntax and I have no idea what you intended this to do (it results in a syntax error).

Explanation

It confuses many MATLAB learners that there are different ways to multiply matrices. These different ways have been explained clearly many times on this forum, and in the documentation:

http://www.mathworks.com/help/matlab/matlab_prog/array-vs-matrix-operations.html

The next topic is how to perform element-wise multiply (or any other element-wise operation) on vectors of different lengths. In short: it is not possible to do this and get a vector the length of the input vectors. What length should the output be? Consider:

[1,2,3] .* [8,9]

as an element-wise operation means:

[1*8,2*9,3*????]

Thus the error. The solution is to either:

pad the vectors to the same length
Orient the vectors orthogonally and operate over every pair of elements. This is what I showed above.

MATLAB: Help me debug this script!

n = 1:35
dataset_pfc_tar_57_n = dataset_pfc_tar_57(n,:)

With n being a vector of length 35, dataset_pfc_tar_57_n is going to have 35 rows and some number of columns that I will call COL

testdata_n = repmat(dataset_pfc_tar_57_n, 8,1)

Those rows are going to be replicated 8 times, giving you 280 rows and COL columns.

pfc_n = testdata_n.*ixCopy

You are multiplying a 280 x COL matrix element-wise by something you have said is 8 x 621. We could hypothesize that COL is 621, so the widths might be equal, but you cannot use .* between a 280 x 621 and an 8 x 621.

Now, if n were a scalar instead of a vector then everything would work out.

Best Answer

Related Solutions

MATLAB: Problem with an equation

MATLAB: Help me debug this script!

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