Concatenating tables with different format

Question

Wesso 2019-1-28

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/441849-concatenating-tables-with-different-format

评论： Walter Roberson 2019-1-28

Hi,

I am concatenating tables in a large loop. all these tables are imported from excel . sometimes Matlab imports the same column as in cells and sometimes as double which is leading to the following errors. For example:

Cannot concatenate the table variable 'TargetBook' because it is a cell in one table and a non-cell in another. the examples are numerous for different columns.

How can I force the concatenation by transforming one column type to fit the precedent table column type in order to concatenate successfully?

in other words

for k = 1:numel(List)
File = fullfile(Base,List(k).name);
Result = readtable(File); 
if k==1
t20172018=Result;
else
t20172018=[t20172018;Result];    
end
end
%% How can I make sure that Result concatenate to t20172018 no matter what the format of the column in Result is?

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Answer 1

Walter Roberson 2019-1-28

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https://ww2.mathworks.cn/matlabcentral/answers/441849-concatenating-tables-with-different-format#answer_358298

detectImportOptions on one of the files that gives you numeric results . Then readtable passing in the detected options each time.

It sounds as if some of the files have text notes in columns intended to be numeric . If so then processing those might be tricky .

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Wesso 2019-1-28

在 MATLAB Online 中打开

I am using the detectImportOptions but without luck

for example, I am getting Cannot concatenate the table variable 'TargetPrimarySICCode' because it is a cell in one table and a non-cell in another.How can I overcome this problem ?

List = dir(fullfile(Base,'*.xlsx'));
Result = cell(1,numel(List));
for k = 1:numel(List)
File = fullfile(Base,List(k).name);
if k==1
Result = readtable(File); %     
t20172018=Result;
opts = detectImportOptions(File);
else
    Result = readtable(File,opts,'ReadVariableNames',false);
    t20172018=[t20172018;Result];  
end
end

Walter Roberson 2019-1-28

detect options first and use them for the first readtable . option detection is better at figuring out needed datatypes so readtable without it can give different types than with it, especially for r2018b with fields that look like times which option detection converts to duration but without detection is a cell array of character .

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