Scatter3, Meshgrid coordinate misalignment. How to fix this?

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Evan
Evan on 6 Jan 2013
Hello,
I have a 3d matrix I want to graph on scatter3. But there's something that's concerning me about the way Matlab parses the meshgrid outputs:
>> a = rand(2, 3, 4)
a(:,:,1) =
0.5557 0.2120 0.9138
0.1844 0.0773 0.7067
a(:,:,2) =
0.5578 0.1662 0.9879
0.3134 0.6225 0.1704
a(:,:,3) =
0.2578 0.0740 0.4024
0.3968 0.6841 0.9828
a(:,:,4) =
0.4022 0.1544 0.1611
0.6207 0.3813 0.7581
>> [x, y, z] = meshgrid(1:2, 1:3, 1:4);
>> [x(:) y(:) z(:) a(:)]
ans =
1.0000 1.0000 1.0000 0.5557
1.0000 2.0000 1.0000 0.1844
1.0000 3.0000 1.0000 0.2120
2.0000 1.0000 1.0000 0.0773
2.0000 2.0000 1.0000 0.9138
2.0000 3.0000 1.0000 0.7067
1.0000 1.0000 2.0000 0.5578
1.0000 2.0000 2.0000 0.3134
1.0000 3.0000 2.0000 0.1662
2.0000 1.0000 2.0000 0.6225
2.0000 2.0000 2.0000 0.9879
2.0000 3.0000 2.0000 0.1704
1.0000 1.0000 3.0000 0.2578
1.0000 2.0000 3.0000 0.3968
1.0000 3.0000 3.0000 0.0740
2.0000 1.0000 3.0000 0.6841
2.0000 2.0000 3.0000 0.4024
2.0000 3.0000 3.0000 0.9828
1.0000 1.0000 4.0000 0.4022
1.0000 2.0000 4.0000 0.6207
1.0000 3.0000 4.0000 0.1544
2.0000 1.0000 4.0000 0.3813
2.0000 2.0000 4.0000 0.1611
2.0000 3.0000 4.0000 0.7581
Say x is 1:2, y is 1:3, z is 1:4, but if you look at the final output, the second value 0.1844 has coordinates (1, 2, 1) when it actually has (2, 1, 1), as you can see from the first part. It looks like the alignment is wrong in this approach.
How would I fix this?
Thank you

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Accepted Answer

Matt J
Matt J on 6 Jan 2013
Use NDGRID instead of MESHGRID.

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