Strings are converted to cells during readtable

조회 수: 130 (최근 30일)
Bill Tubbs
Bill Tubbs 2022년 6월 10일
답변: Adam Danz 2024년 1월 4일
I am incrementally saving data to a csv file which includes strings:
data = table("string1", "string2");
writetable(data, "data.csv");
Later on:
data_from_file = readtable('data.csv')
data_from_file =
1×2 table
Var1 Var2
___________ ___________
{'string1'} {'string2'}
Note that the data are now char arrays in cells.
This is causing lots of problems, for example when I try to join the old data with the new:
new_data = table("string1", "string2");
data = outerjoin(data_from_file, new_data, 'MergeKeys', true)
Error using tabular/outerjoin (line 152)
Left and right key variables 'Var1' and 'Var1' are not comparable because one is
a non-cell.
Is there a way to avoid this problem or convert the chars back to strings after readtable?
  댓글 수: 2
KSSV
KSSV 2022년 6월 10일
Show us your new_data.
Bill Tubbs
Bill Tubbs 2022년 6월 10일
E.g.
new_data = table("string1", "string2");

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채택된 답변

Stephen23
Stephen23 2022년 6월 10일
편집: Stephen23 2022년 6월 10일
The simple solution is to specify the TEXTTYPE option when importing:
data = table("string1", "string2");
writetable(data, "data.csv");
data_from_file = readtable('data.csv', 'TextType','string')
data_from_file = 1×2 table
Var1 Var2 _________ _________ "string1" "string2"

추가 답변 (2개)

Adam Danz
Adam Danz 2024년 1월 4일
When using the readtable(filename,opts,Name,Value) syntax, only a limited number of name-values pairs are available as input arguments and TextType is not one of them. If you are using the import options object and would like to enforce strings for text type, specify this name-value pair as an argument in detectImportOptions()
opts = detectImportOptions(filename,'TextType','string');
T = readtable(filename,opts)

KSSV
KSSV 2022년 6월 10일
You can convert cell into a string and then use join.
data = table("string1", "string2");
writetable(data, "data.csv");
data_from_file = readtable('data.csv') ;
for i = 1:width(data_from_file)
data_from_file.(i) = string(data_from_file.(i)) ;
end
new_data = table("string3", "string4");
data = outerjoin(data_from_file, new_data, 'MergeKeys', true)

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