MATLAB: How to “readtable” with a CSV file when table elements have newlines or double quotation marks

breakcsvdetectimportoptionsdouble-quoteslineMATLABquotequotestringreadtablewritetable

I have a table, "DataTable", in a CSV file with elements that are strings containing line breaks, double quotes, and commas. When I read the table from the CSV file, the table is not the same as the one I had originally.

Why does this happen and how can I read my table using a CSV file?

Best Answer

Based on the definition of the CSV format, fields containing line breaks (CRLF), double quotes, and commas should be enclosed in double-quotes.

When reading from the CSV, you can explicitly tell "readtable" the format of the file. This option's workflow is documented at the link below:

https://www.mathworks.com/help/matlab/ref/readtable.html#bvghccx

This is illustrated as follows:

>> opts = detectImportOptions('DataTable.csv');
>> T = readtable('DataTable.csv',opts)

Related Solutions

MATLAB: How to “writetable” with a CSV file when table elements have newlines or double quotation marks

Based on the definition of the CSV format, fields containing line breaks (CRLF), double quotes, and commas should be enclosed in double-quotes.

In order to write the original table to CSV format, you can add the "QuoteStrings" flag to "writetable". The flag is documented at the link below:

https://www.mathworks.com/help/matlab/ref/writetable.html#input_argument_d0e1111341

This is illustrated as follows:

>> writetable(DataTable, 'DataTable.csv','QuoteStrings',true);

Then, when reading from the CSV, you should explicitly tell "readtable" the format of the file. This option's workflow is documented at the link below:

https://www.mathworks.com/help/matlab/ref/readtable.html#bvghccx

This is illustrated as follows:

>> opts = detectImportOptions('DataTable.csv'); 
>> T = readtable('DataTable.csv',opts)

MATLAB: How to specify the column headers while reading in a CSV file using ‘readtable’

The 'VariableNamesLine' property can be used to specify this. Please refer to the example snippet below.

%Import the options of the csv file
opts=detectImportOptions('sample.csv');
%Defines the row location of channel variable name
opts.VariableNamesLine = 4;
%Specifies that the data is comma seperated

opts.Delimiter =','; %Specifies that the data is comma seperated
%Read the table
t = readtable('sample.csv',opts, 'ReadVariableNames', true);

As mentioned in the link below, the properties 'VariableNamesRange' and 'VariableNamesLine' can be specified only if the 'ReadVariableNames' argument is set to 'true'. Refer to the second subsection of 'Name-Value Pair Arguments' to learn more.

https://www.mathworks.com/help/releases/R2019a/matlab/ref/readtable.html

Best Answer

Related Solutions

MATLAB: How to “writetable” with a CSV file when table elements have newlines or double quotation marks

MATLAB: How to specify the column headers while reading in a CSV file using ‘readtable’

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