How can I keep the first two elements from CSV values in a string

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Gustavo Schwartz 2024-10-1，15:49

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评论： Gustavo Schwartz 2024-10-2，9:05

I have a Table where one of the columns contains text elements separated by commas. I want to keep the first element (if there is only one) or the first two (if the are more than one). There also could be empty lines. For example, from:

abcd, efgh, tyui

[]

lkjh, poiu

wert

I want to get

abcd, efgh

[]

lkjh, pou

wert

I know how to do this with a for loop. But the idea would be to use regular expressions or something similar to accelerate the process. The Table has almost 2M elements.

Any suggestion would be of great help. Thanks.

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Answer 1

Stephen23 2024-10-2，6:35

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编辑：Stephen23 2024-10-2，6:36

在 MATLAB Online 中打开

S = ["";"philosopher,historian,writer,political activist,literary critic";"philosopher";"philosopher,writer"]
S = 4x1 string array
    ""
    "philosopher,historian,writer,political activist,literary critic"
    "philosopher"
    "philosopher,writer"
T = regexp(S,'^[^,]*(,[^,]+)?','match','once','emptymatch')
T = 4x1 string array
    ""
    "philosopher,historian"
    "philosopher"
    "philosopher,writer"

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Gustavo Schwartz 2024-10-2，9:05

Thanks Stephen23! This is exactly what I needed.

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Answer 2

Walter Roberson 2024-10-1，23:17

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https://ww2.mathworks.cn/matlabcentral/answers/2156785-how-can-i-keep-the-first-two-elements-from-csv-values-in-a-string#answer_1525580

在 MATLAB Online 中打开

FilteredData = regexp(YourTable.ColumnName, '^[^,]+(,\s+[^,]+)?', 'match', 'once');

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Gustavo Schwartz 2024-10-2，6:01

Thanks, Walter, for your soon response. This regexp works to extract the words before the first comma, but I need to extract the words before the second comma (if there are more than one). Suppose I have:

"philosopher,historian,writer,political activist,literary critic"

"philosopher"

"philosopher,writer"

I want to get

"philosopher,historian"

"philosopher"

"philosopher,writer"

I would appreciate if you can provide a regexp to solve this problem.

Gustavo Schwartz 2024-10-2，6:18

Aparently, this regexp works:

regexp(Table.Colum, '^[^,]*(?:,[^,]*)?','match')

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