Dimensionality error with plot

Hi, I would like to plot a snippet of pressureData, which is a 3 dimensional matrix, as follows:

tDim=length(pressureData(1,1,:)); t=zeros(1,tDim); dt=0.01;

for ii=1:tDim % Build time axis for plot

t(ii)=ii*dt;

end

plot(t,pressureData(1,1,:))

This returns an error saying "Error using plot. Data cannot have more than two dimensions."

When I output the vector pressureData(1,1,:) in the command window, the output looks like this:

ans(:,:,1) =

-0.0038

ans(:,:,2) =

-0.0042

etc.

The data type for pressureData is double, so I'm not sure why I am getting this odd output. Any ideas? Thanks in advance!

[VBBV]

 Pdata = reshape(pressureData(1,1,:),1,[])
plot(t,Pdata)

[VBBV]

Use reshape function to reduce the multidimensional matrix into vector since plot function uses vectors to graph data

[Andrew]

@VBBV that does fix the plotting issue. How would I then reform the matrix back into its original 3D configuration?

[Andrew]

The pressureData matrix is a 50x50x5000 matrix and I would like to keep it that way.

[the cyclist]

Neither of the solutions so far (as I write this) change the size of pressureData.

Answer 1

[the cyclist]

I understand your confusion. pressureData(1,1,:) is a vector in the sense that it only has elements along one dimension (the 3rd dimension), but it is still a three-dimensional MATLAB array because it is 1x1xtDim.

There are a couple possible solutions. Probably the easiest is to use the squeeze function to remove the dimensions that have length 1.

plot(t,squeeze(pressureData(1,1,:)))

You could also use the reshape or permute functions to manipulate the shape of the array.

[Andrew]

@the cyclist got it. Thank you!

[the cyclist]

The size of pressureData doesn't really matter. The fact remains that

pressureData(1,1,:)

is a 1x1x5000 array, which is 3-dimensional. MATLAB will not treat that as a vector for plotting purposes, which is why you get the error. But

squeeze(pressureData(1,1,:))

is a 5000x1 vector, which will plot.

[Andrew]

@the cyclist thank you!

Answer 2

[VBBV]

Pdata = reshape(pressureData(1,1,:),1,[])
plot(t,Pdata)

[VBBV]

The original 3D remains in the pressureData variable itself visible in workspace. For plotting purposes a variable is assigned (i.e. Pdata in my answer) after reshaping the data. You can directly apply the reshape function on presssureData itself.

[Andrew]

@VBBV thank you!