Extracting specific data for multiple mat files

2022 8 22
2 个回答
更新时间：2022 8 24
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1 个投票

Hello. I am having around 1800 mat files that are the output of Venlodyne lidar. I have converted all of them to the PCD format as well. So, I want to extract the specific data, which is determined by specific row or column, from those files. Please help me with this question. Thank you so much for your support!

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Chunru
Chunru 2022-8-22
Attach some sample data.
Thanh
Thanh 2022-8-22
Sorry for not adding files. Here are some files for instance.

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回答（2 个）

Chunru
Chunru 2022-8-22
Ran in:

1 个投票

Ran in:
fn = dir("save*.mat")
fn = 2×1 struct array with fields:
name folder date bytes isdir datenum
for i = 1:length(fn)
matobj{i} = matfile(fn(i).name)
matobj{i}.PCD % Then you can access to any portion of data and assign the results to a variable
end
matobj = 1×1 cell array
{1×1 matlab.io.MatFile}
ans =
pointCloud with properties: Location: [16×1808×3 double] Count: 28928 XLimits: [-10.5304 19.9285] YLimits: [-5.1332 9.1553] ZLimits: [-2.5690 5.3415] Color: [] Normal: [] Intensity: [16×1808 uint8]
matobj = 1×2 cell array
{1×1 matlab.io.MatFile} {1×1 matlab.io.MatFile}
ans =
pointCloud with properties: Location: [16×1808×3 double] Count: 28928 XLimits: [-10.5543 19.8885] YLimits: [-5.1543 9.2809] ZLimits: [-2.5587 5.3218] Color: [] Normal: [] Intensity: [16×1808 uint8]
Thanh
Thanh 2022-8-23
编辑：Thanh 2022-8-23

1 个投票

Thank you SIr for your answer. I tried to use the code to extract data of all mat files in column 1706 but it pops up another error "Index in position 2 exceeds array bounds. Index must not exceed 1." Can you help me with this error please? You can see my code adjustment here. Thank a lots!
fn = dir("save*.mat")
for i = 1:length(fn)
matobj{i} = matfile(fn(i).name)
dataPCD = matobj{i}.PCD % Then you can access to any portion of data and assign the results to a variable
Data = dataPCD(:,1706)
end

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Chunru
Chunru 2022-8-23
What data you want to extract? dataPCD is an object of pointCloud. Which part of the data you want to extract?
pointCloud with properties:
Location: [16×1808×3 double]
Count: 28928
XLimits: [-10.5304 19.9285]
YLimits: [-5.1332 9.1553]
ZLimits: [-2.5690 5.3415]
Color: []
Normal: []
Intensity: [16×1808 uint8]
Thanh
Thanh 2022-8-23
编辑：Thanh 2022-8-23
I want to extract the y-value of column 1706 of Location data. I tried with the following code but the ouput is not as same as in Location data which I manually picked from those files.
fn = dir("save*.mat")
for i = 1:length(fn)
matobj{i} = matfile(fn(i).name)
dataPCD = matobj{i}.PCD % Then you can access to any portion of data and assign the results to a variable
Data(:,i) = dataPCD.Location(:,1706)
end
Chunru
Chunru 2022-8-23
The location data has the following 3D format:
Location: [16×1808×3 double]
Which slice of data you want to extract? You might want to specify 3 indeces instead of 2.
Thanh
Thanh 2022-8-24
Thank you Sir so much! I have extracted the data

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R2022a

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Thanh
Thanh
2022-8-22

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Chunru
Chunru
2022-8-24

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