Undefined function or method fitlm for input arguments of type double

The error message "Undefined function or method 'fitlm' for input arguments of type 'double'" typically occurs when you try to use the function 'fitlm' on a variable of type 'double' that does not support this operation.

The function 'fitlm' is part of the Statistics and Machine Learning Toolbox in MATLAB and is used for fitting linear regression models. This function requires a table or dataset as input, not a double.

To resolve this issue, you can convert your data into a table or dataset format before applying the 'fitlm' function. Here is an example:

% Create a table from your double input data
data = [1, 2, 3, 4, 5]; % Example input data
tableData = array2table(data);

% Fit a linear regression model using the table data
model = fitlm(tableData);

In this example, the 'array2table' function is used to convert the double input data into a table format. Then, the 'fitlm' function is applied to the table data to fit a linear regression model.

Make sure to have the Statistics and Machine Learning Toolbox installed and loaded in MATLAB before using the 'fitlm' function