MATLAB Answers

Bizzy Dy

How to replace char 'null' in number 0?

Asked by Bizzy Dy
on 9 Aug 2018
Latest activity Commented on by Guillaume
on 9 Aug 2018
Hi! I`ve got a problem with using plot function cause there is some 'null's (char type) in my data files . So i would like to change/replace that nulls in 0 (num) . Could someone help to find useful function or to offer other solution.


Guillaume is right: fix the problem when it occurs, rather than trying to write hack code to "fix" it later. Upload a sample data file by clicking the paperclip button.
on 9 Aug 2018
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2 Answers

Answer by Guillaume
on 9 Aug 2018
Edited by Guillaume
on 9 Aug 2018
 Accepted Answer

It's much easier to read your file with readtable (which also does not require any toolbox). It is trivial with readtable to convert the 'null' to 0 and read everything else as number.
t = readtable('result_3259_m.tsv', 'FileType', 'text', 'TreatAsEmpty', 'null', 'EmptyValue', 0);
t.time = datetime(t.time, 'InputFormat', 'yyyy-MM-dd''T''HH:mm:ss''Z''');
For further processing you may even want to convert the table to a timetable
I would also recommend that you do not extract the table columns into variables with meaningless names. Just use the table variables directly:
plot(t.time, t.input_flowrate_bezm, 'DatetimeTickFormat', 'dd.MM, HH:mm');

  1 Comment

Thank you so much!

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Answer by Ameer Hamza
on 9 Aug 2018

The image shows a struct which char arrays as fields. You can use strrep() to replace the elements of a char array. Although it will still not work with the plot() function because the elements are char arrays, not numeric values. You might need to use str2num() to convert char values t numeric before using plot().


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