MATLAB Answers

0

how to separate strings from a datatable?

Asked by Jonathan Bijman on 11 Jun 2019
Latest activity Commented on by Walter Roberson
on 12 Jun 2019
Hello everyone
I'm trying to separate strings from a datatable, of one specific column that contains this for instance:
2019-04-22 Clean A8
and I want to separate date from the strings.
I used this commands:
time=Clean(:,1);
str=string(time);
tiempo=strsplit(str);
But when I apply the last one appears this error:
First input must be either a character vector or a string scalar.
Which I don´t get it, because there are string in there? Aren´t they?
Do I have to work with datatable or cells?
Please help

  1 Comment

I would think the more fundamental question is how you got into this situation to begin with. Are you reading a file? If so can you use detectimportoptions and then readtable to read the data in correctly?

Sign in to comment.

2 Answers

Answer by Walter Roberson
on 12 Jun 2019
 Accepted Answer

tiempo = arrayfun(@strsplit, str, 'uniform', 0);

  8 Comments

I wrote this
time=Clean(:,1);
r=string(time);
tiempo = arrayfun(@strsplit, r, 'uniform', 0);
tiempo_1 =arrayfun(@(V) V{1}, tiempo, 'uniform', 0)
And appears the same thing:
1 x 3 string
And when I click on it, appers the same as the picture.
The idea is the date appears as one column separate from the other ones, as a table or array (I dunno what's better)
pic.jpg
dpb
on 12 Jun 2019
"I get a cell with 1 x 3 strings. But how can I extract only the date from there? "
Look at the content of the cell array...as you asked to split on delimiters and your input array consists of three substrings, (surprise) strplit returned each substring in each row of a three-column cell array.
Hence, the first column contains the date, the second two the subsequent string data fields.
tiempo{:,1}
contains the time string.
cellfun(@(V) V{1}, tiempo, 'uniform', 0)

Sign in to comment.


Answer by dpb
on 12 Jun 2019

As the error message says, strsplit only operates on the strings class or char arrays--it can't handle either cell strings (the reason for which I do not understand) or the result of a table operation that returns a table...
>> Clean={'2019-04-22 Clean A8'}; % sample data
>> Clean=cell2table(Clean) % convert to table (if that is what mean with datatable; we're guessing)
Clean =
table
Clean
_____________________
'2019-04-22 Clean A8'
>> Clean(:,1) % address the variable with numeric subscripting--returns another table
ans =
table
Clean
_____________________
'2019-04-22 Clean A8'
>> strsplit(Clean(:,1)) % and strsplit can't deal with that...as you already found out
Error using strsplit (line 80)
First input must be either a character vector or a string scalar.
>> Clean{:,1} % dereference with curlies {} to get content instead of table--
ans =
1×1 cell array
{'2019-04-22 Clean A8'}
>> strsplit(Clean{:,1}) % but, as error says it can't handle cellstr, either... :(
Error using strsplit (line 80)t
First input must be either a character vector or a string scalar.
>> strsplit(char(Clean{:,1})) % but it can handle a char() array as the message says
ans =
1×3 cell array
{'2019-04-22'} {'Clean'} {'A8'}
>> strsplit(string(Clean{:,1})) % or a string...
ans =
1×3 string array
"2019-04-22" "Clean" "A8"
>> strsplit(string(Clean(:,1))) % but notice you have to dereference the content or...
Error using string
Conversion to string from table is not possible.
>>

  4 Comments

Show 1 older comment
dpb
on 12 Jun 2019
Well, dunno...
What does
which -all string
return?
Also, it still isn't absolutely clear what you started with--I made some assumptions that your original data was in a cellstr based on the error and that you were using a table because you used the word "datatable" but whether that means a MATLAB table class variable or not is not totally clear.
Now, above, it does appear to have started with a cell array and turned it to a table. The second assignment to the variable tiempo negates the first entirely--there's no point in it.
If I reproduce that with the table I created here, it works just fine...which Matlab release are you using? string is a relatively recent introduction.
Also, post what
whos Clean*
returns as well as
whos tiempo
after the second definition.
@Jonathan Bijman: please upload the variable tiempo in a .mat file by clicking the paperclip button.

Sign in to comment.