reading the data from a csv file with headers

Hi, I have a csv file similar to this:

 a    b   c    d
 12  35   86   4

How can I read the data for one of the headers? Knowing the name of the file and the headers, is it possible to read the number associated with that header?

Answer 1

[Star Strider]

If you have R2013b or later, use the readtable (link) function.

Example —

To get the data in ‘c’:

Tbl = readtable('YourFile.csv');
cv = Tbl.c;                                                              % Easiest, Most Direct

Alternatively, you can recover the column associated with each header (column name) by using ‘Properties.VariableNames’ to retrieve them. Then use strcmp to get the logical vector of matching column names, and find to get the column number. :

VarNames = Tbl.Properties.VariableNames;                                 % Recover Variable Names (Column Titles)
ColIdx = find(strcmp(VarNames, 'c'));                                    % Return Column Index For Variable Name ‘c’

Then use ‘ColIdx’ to access the column data in variable ‘c’.

Experiment to get the result you want.

[hoda kazemzadeh]

That works! Thanks a lot

[Star Strider]

As always, my pleasure!

[hoda kazemzadeh]

Hello, regarding this discussion I encounter a problem. for the parameters of numeric array I use

 t=readtable('file.csv')
 c=t.serialnum

and some parameters contain characters so I use :

 c=char(t.Name)

there is a parameter which can be array of char OR numeric array . what can I use to read from the table (and later I will write in the medadata of wav file) to adopt with both cases?

[Star Strider]

I do not understand.

What are you doing, and what is the file you are importing?

[hoda kazemzadeh]

I have a csv file and I need to read that file and I use in the title of wav file which I write using audiowrite.

Tb = readtable('configuration.csv');
TypeCapteur=char(Tb.TypeCapteurR);
Nom=char(Tb.NomR);
NumeroSerie=char(Tb.NumeroSerieR);
ConversionFactor=Tb.CorrectionCalibrationR;
filename=[TypeCapteur,'_', Nom,'_', NumeroSerie,'_', num2str(ConversionFactor),'.wav'];
infotitle=filename 
audiowrite(filename,X,48000,'BitsPerSample',24,'Title',infotitle);

Some of the parameters are numeric array like Conversionfactor and some others contain numbers and letters that I read using 'char'. For the parameter "NumeroSerie" it can happen both cases (numeric array, string array or characters and numbers). If I have characters and numbers that works but if it was a number and read it using char(...) I got an error and vice versa.

[Star Strider]

I do not have your file, and I still do not undersrtand the problem.

[hoda kazemzadeh]

I have the parameters in csv file. 'Name' and 'Serialnum' and 'Cfactor are the headers.

'Serialnum' can be number or number/letter. 'Name' contains only letters and 'Cfactor' is a number. I read them and I write in the filename of wav file.

 Tb = readtable('configuration.csv');
 c=char(Tb.Name)
 b=Tb.Cfactor

filename=[Name,'_', serialnum,'_',num2str(Cfactor),'.wav'];
audiowrite(filename,X,48000,'BitsPerSample',24);

my question is that what I have to use for 'serialnum' that can be numeric array or char array to work in both cases.

I hope it was clear.

[Star Strider]

Try this:

snstr = num2str(serialnumber);
cfstr = num2str(Cfactor);
filename = sprintf('%s_%s_%s.wav', Name, snstr, cfstr)

I have no idea what your data are, so I cannot experiment with this.

[hoda kazemzadeh]

This is the csv file. serialnumber is not always array of numbers. it may contains letters (as it has in the file) so num2str does not work for that. my problem is that serialnumber could be as both types (only numbers or numbers/letters) and it depends on the type of the sensor that may change.

[Star Strider]

The ‘serialnumber’ is a hexadecimal number that is read as a string in the cell array. You can retrieve it as a string easily, and you do not have to do any conversions:

Tb = readtable('configuration.csv');
Vars = Tb.Properties.VariableNames;
serialnumidx = find(contains(Vars,'SerialNumber'));
serialnumv = Tb{1,serialnumidx};
serialnum = serialnumv{1};

serialnum =
    '231A'

I have no idea how you are getting the data from your table, or which serial number you want (there are 2 in this file). This is how I would do it.