stepwiselm() function is not taking the last column of table as Response variable

I have imported a table with size 2000*85. Table name is data2000.

when I use the command m1 = stepwiselm(dataset2000), it is giving me the following error.

/*

m1 = stepwiselm(data2000)

Error using classreg.regr.FormulaProcessor (line 298)

Cannot determine the response variable.

Error in classreg.regr.LinearFormula (line 48)

f = [e-mail](varargin{:});

Error in classreg.regr.TermsRegression/createFormula (line 857)

formula =

classreg.regr.LinearFormula(modelDef,varNames,responseVar,intercept,link);

Error in LinearModel/createFormula (line 880)

formula = classreg.regr.TermsRegression.createFormula(supplied,modelDef, ...

Error in LinearModel.stepwise (line 70)

start = LinearModel.createFormula(supplied,start,X, ...

Error in stepwiselm (line 100)

model = LinearModel.stepwise(X,varargin{:});

*/

Then I tried the command

m1 = stepwiselm(data2000,Label) and getting the following error

/*

Undefined function or variable 'Label'.*/

Please help. I have attached screenshot as reference.

Thanks in advance

[Ive J]

Can you upload your data mat file?

[Pavithra Naik]

Hello, This is not a mat file It is excel data. I am uploading the file for your reference

Thank you

Answer 1

[Ive J]

The issue stems from variable Timestamp, which is of class datetime. You need to first convert it to numeric type:

data = readtable('data2000.xlsx', 'TextType', 'string');
data.Timestamp = datenum(data.Timestamp);

Also I see you have some string variables, better to include them as categorical when calling the function:

model = stepwiselm(data, 'CategoricalVars', ...);

[Pavithra Naik]

Hi Ive,

I converted Timestamp to numeric type using the instructions you suggested and then tried developing the model . It is working properly now. Thank you very much for helping. I was really stuck and your suggestion helped me to proceed further.

Thanks again.

Commands I used are :

data = readtable('data2000.xlsx', 'TextType', 'string');

data.Timestamp = datenum(data.Timestamp);

model1 = stepwiselm(data);