How do I extract data from a structure and put them all in one single array?

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Luis Ricardo Rivera Goitia 2023-4-12

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评论： Image Analyst 2023-4-12

I have a 1X31 struct with two fields, I would like to extract all the data from the second one, and put them all in one single array.

How can I do that?

Here are some images to illustrate how they are arranged.

So what I want to do is to create an array that contains dataTT(1).Data + dataTT(2).Data + ... dataTT(n).Data

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Answer 1

Stephen23 2023-4-12

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https://ww2.mathworks.cn/matlabcentral/answers/1945944-how-do-i-extract-data-from-a-structure-and-put-them-all-in-one-single-array#answer_1214469

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https://www.mathworks.com/matlabcentral/answers/1656435-tutorial-comma-separated-lists-and-how-to-use-them

S = vertcat(dataTT.Data)

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Stephen23 2023-4-12

编辑：Stephen23 2023-4-12

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I guess your next request will be to convert that string data into numeric... Here are some approaches:

S = ["{1.23,4.56,7.89}";"{9.87,6.54,3.21}";"{12.3,45.6,78.9}";"{98.7,65.4,32.1}"]
S = 4×1 string array
    "{1.23,4.56,7.89}"
    "{9.87,6.54,3.21}"
    "{12.3,45.6,78.9}"
    "{98.7,65.4,32.1}"
M = sscanf([S{:}],'{%f,%f,%f}',[3,Inf]).'
M = 4×3
    1.2300    4.5600    7.8900
    9.8700    6.5400    3.2100
   12.3000   45.6000   78.9000
   98.7000   65.4000   32.1000
M = double(split(replace(S,["{","}"],''),','))
M = 4×3
    1.2300    4.5600    7.8900
    9.8700    6.5400    3.2100
   12.3000   45.6000   78.9000
   98.7000   65.4000   32.1000

Luis Ricardo Rivera Goitia 2023-4-12

Excelent! It worked Thx

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Answer 2

Image Analyst 2023-4-12

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编辑：Image Analyst 2023-4-12

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You forgot to attach your data in a .mat file with the paperclip icon so we can't try it with your data. You can try these things:

v = {dataTT.Topic}

or

v = vertcat(dataTT.Topic)

Same for the Data field

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Luis Ricardo Rivera Goitia 2023-4-12

Thx a lot it worked using v = vertcat(data.Topic) or vertcat(dataTT.Data).

Image Analyst 2023-4-12

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You're welcome. Just additional info to extend this into future situations you might encounter: If the numbers were single numbers, not cell arrays of 3 numbers then you could do

v = [structName.fieldName] % Concatenate all fields into a single vector.

For a real world example, where mask is a binary image with several "blobs" that you want to measure the area of:

props = regionprops(mask, 'Area'); % Returns a structure with "Area" as a field of the structure.
allAreas = [props.Area]; % Concatenate all areas into a single double vector.

I use it that way all the time.

If my replies helped you, perhaps you could click the "Vote" icon. 🙂

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