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SKG
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Reading csv file NaN and NaT problem

Asked by SKG
on 31 Oct 2018
Latest activity Commented on by Jeremy Hughes on 31 Oct 2018
Hi all,
I am trying to make a csv file read.File is located in "file path". The Variable Names is in line 2.
detectImportOptions(filepath);
opts.DataLines=[1,Inf];
T = readtable(filepath,opts);
I can read the file but the problem is that some of the variables are changing to NaT or NaN, is it possible to set on line 2 (where the variable names are located) to character before executing readable function?

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3 Answers

Answer by Jeremy Hughes on 31 Oct 2018

Based on the description, I think this is what you'd want. Without an attached file, I cannot say more.
opts = detectImportOptions(filepath);
opts.VariableNamesLine = 2;
opts.DataLines=[3,Inf];
T = readtable(filepath,opts,'ReadVariableNames',true);

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Answer by dpb
on 31 Oct 2018

detectImportOptions(filepath);
You didn't save the output of detectImportOptions so you don't have an import options object at this point.
Hence,
opts.DataLines=[1,Inf];
simply creates the one element in the struct named opts that you passed to readtable but everything else is its default, NOT what the detectImportOptions function would have divined to be the characteristics of the file.
Try
opts=detectImportOptions(filepath);
T = readtable(filepath,opts);
first before resorting to anything more exotic; generally the automagic scanning routines are able to infer "who's who in the zoo" without human intervention.
You can use setvartype, yes, if it turns out to be needed as well as setting the specific time format string, but try the above first.

  5 Comments

There's no way to have one row be text and the others numeric. Tables are homogeneous in the "row" direction. This is why the fields are being converted to NaN or NaT.
Try my answer above and see if that gives you closer to what you expect.
SKG
on 31 Oct 2018
I already tried, it is not working
dpb
on 31 Oct 2018
ONE MORE TIME!!!!
We can't help you if you won't show us what the input data format actually is.
Attach a few lines of the data file that illustrates the format and where you have a problem.

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Answer by SKG
on 31 Oct 2018

Solved it:
opts = detectImportOptions(filepath); opts.DataLines=[1,Inf ]; opts.VariableTypes(1, 1:end) = {'char'};

  1 Comment

Note, this will set all the data you import to be cells of character vectors, no numbers.

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