Extract field of struct array to new array

Question

I have a struct, which has 2 fields: time and pose. I have multiple instances of this struct composed in an array, so an example of this is:

poses(1)
    -time = 1
    -pose = (doesn't Matter)
poses(2)
    -time = 2
    -pose = (doesn't Matter)
poses(3)
    -time = 3
    -pose = (doesn't Matter)
...

Now when I print this:

 poses.time

I get this:

ans =
      1
ans =
      2
ans =
      3

How can I take that output and put it into a vector?

Gunther Struyf · Accepted Answer · 2012-08-22 23:34:46Z

18

Use brackets:

timevec=[poses.time];

tricky matlab, I know I know, you'll just have to remember this one if you're working with structs ;)

edited Aug 22, 2012 at 23:34

answered Aug 22, 2012 at 23:28

Gunther Struyf

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6 Comments

zml Over a year ago

What about string values ? if poses.time is ans="1" ans="2" ans="3", timevec=[poses.time] would give "123". Is there a way to fix this ?

Gunther Struyf Over a year ago

@zml "123" is already an array, try indexing it and see for yourself. If you want them really separate, you'll need a cell array: timevec={poses.time}. See here for more on string arrays

Eric Over a year ago

What if poses is 2d?

Gunther Struyf Over a year ago

@Eric the brackets [...] on [poses.time] will concatenate it in a 1D array, regardless of the size of poses (as long as the actual values cán be put in a 1D array). Use reshape to get it back into the shape you started with

Eric Over a year ago

So in general, reshape(mystruct.member, size(mystruct))?

|

saastn · Accepted Answer · 2017-01-20 23:03:38Z

2

For cases that the field values are vectors (of same size) and you need the result in a matrix form:

posmat = cell2mat({poses.pose}');

That returns each pose vector in a different row of posmat.

answered Jan 20, 2017 at 23:03

saastn

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