how to separate strings from a datatable?

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

[Peter Perkins]

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?

Answer 1

[Walter Roberson]

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

[Jonathan Bijman]

When I apply the last command, I get a 298 x 1 cell array, and all says:

tiempo = arrayfun(@strsplit, str, 'uniform', 0)
tiempo =
  298×1 cell array
    {1×3 string}
    {1×3 string}
    {1×3 string}
    {1×3 string}
    {1×3 string}

how can I see, for instance, only the date 2019-04-22?

[Jonathan Bijman]

these are the commands I wrote:

time=Clean(:,1);
str=string(time);
tiempo = arrayfun(@strsplit, str, 'uniform', 0);

[Jonathan Bijman]

Thanks Walter! I already realize that it works.

Thank u so much =)

[Jonathan Bijman]

From the last command

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

I get a cell with 1 x 3 strings. But how can I extract only the date from there?

[Walter Roberson]

arrayfun(@(V) V{1}, tiempo, 'uniform', 0)

[Jonathan Bijman]

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)

[dpb]

"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.

[Walter Roberson]

cellfun(@(V) V{1}, tiempo, 'uniform', 0)

Answer 2

[dpb]

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. 
>> 

[Jonathan Bijman]

I put these commands:

Clean_1=cell2table(Clean);
tiempo=Clean_1(:,1);
tiempo=Clean_1{:,1};
strsplit(string(tiempo{:,1}));

and appears this error:

Error using string
No constructor 'string' with matching signature found.
Error in Prueba_1 (line 29)
strsplit(string(tiempo{:,1}));

If I turned data into a table, why does appear this error?

I didn´t say it, but it's a lot of data with the same structure

date Clean Letter

[dpb]

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.

[Stephen23]

@Jonathan Bijman: please upload the variable tiempo in a .mat file by clicking the paperclip button.

[Jonathan Bijman]

@Stephen Cobeldick