Why does str2double command return NaN? What type of array should I convert into for running fitlm command??

Hi all,

This issue is holding me over two hours so I want to ask how to fix it.

My dataset is a 48X1 cell array, and want to run comman fitlm to derive AR(1) process - yes, it is time series data.

x =

  48×1 cell array

    {[  7.9614]}
    {[  6.6333]}
    {[  6.5029]}
    {[  5.9425]}
    {[  1.8100]}
    {[ -0.4337]}
    {[ -2.9584]}
    {[ -1.9444]}
    {[ -0.9811]}
    {[ -1.2110]}
    {[  0.0166]}
    {[ -0.7115]}
    {[ -1.4040]}
    {[  1.0919]}
    {[  1.8558]}
    {[ 11.2266]}
    {[  0.3792]}
    {[ -1.9763]}
    {[ -4.0722]}
    {[-16.7206]}
    {[ -6.4143]}
    {[ -5.3453]}
    {[ -2.5355]}
    {[  1.8669]}
    {[  3.4383]}
    {[  5.9412]}
    {[  5.4722]}
    {[ 11.5480]}
    {[  6.3237]}
    {[  5.7294]}
    {[  4.7529]}
    {[  4.0313]}
    {[  3.4431]}
    {[  1.5301]}
    {[ -0.4894]}
    {[ -7.7308]}
    {[ -3.1757]}
    {[ -8.3770]}
    {[ -1.9913]}
    {[  0.7572]}
    {[  7.9531]}
    {[ 16.1144]}
    {[ 14.1777]}
    {[ 13.6904]}
    {[  9.4649]}
    {[  9.7910]}
    {[  5.4224]}
    {[  1.8821]}

I want to conert the dataset x to run a regression but don't know which type of data I should convert to. In the first place, I tried str2double but it returned only 48 NaNs. I tried to cell2mat but it didn't work either. What command should I use for running fitlm?

Answer 1

[Star Strider]

Of course str2double returned NaN for all of them because none of them are strings or character vectors.

I suspect there are concatenation brackets missing. That aside, the easiest way to do what you want is to use cell2mat —

x = [{[  7.9614]}
    {[  6.6333]}
    {[  6.5029]}
    {[  5.9425]}
    {[  1.8100]}
    {[ -0.4337]}
    {[ -2.9584]}
    {[ -1.9444]}
    {[ -0.9811]}
    {[ -1.2110]}
    {[  0.0166]}
    {[ -0.7115]}
    {[ -1.4040]}
    {[  1.0919]}
    {[  1.8558]}
    {[ 11.2266]}
    {[  0.3792]}
    {[ -1.9763]}
    {[ -4.0722]}
    {[-16.7206]}
    {[ -6.4143]}
    {[ -5.3453]}
    {[ -2.5355]}
    {[  1.8669]}
    {[  3.4383]}
    {[  5.9412]}
    {[  5.4722]}
    {[ 11.5480]}
    {[  6.3237]}
    {[  5.7294]}
    {[  4.7529]}
    {[  4.0313]}
    {[  3.4431]}
    {[  1.5301]}
    {[ -0.4894]}
    {[ -7.7308]}
    {[ -3.1757]}
    {[ -8.3770]}
    {[ -1.9913]}
    {[  0.7572]}
    {[  7.9531]}
    {[ 16.1144]}
    {[ 14.1777]}
    {[ 13.6904]}
    {[  9.4649]}
    {[  9.7910]}
    {[  5.4224]}
    {[  1.8821]}]

x = 48×1 cell array
    {[ 7.9614]}
    {[ 6.6333]}
    {[ 6.5029]}
    {[ 5.9425]}
    {[ 1.8100]}
    {[-0.4337]}
    {[-2.9584]}
    {[-1.9444]}
    {[-0.9811]}
    {[-1.2110]}
    {[ 0.0166]}
    {[-0.7115]}
    {[-1.4040]}
    {[ 1.0919]}
    {[ 1.8558]}
    {[11.2266]}

xv = cell2mat(x)

xv = 48×1

7.9614 6.6333 6.5029 5.9425 1.8100 -0.4337 -2.9584 -1.9444 -0.9811 -1.2110

xv = [x{:}].'                           % Alternative Approach

xv = 48×1

7.9614 6.6333 6.5029 5.9425 1.8100 -0.4337 -2.9584 -1.9444 -0.9811 -1.2110

See if that works in your application.

.

[Seraphic]

@Star Strider Thanks so much. Cell2mat worked. By the way, just an hour ago when I tried cell2mat, it didn't work but it is working at this moment. Also appriecate your explanation.

[Star Strider]

My pleasure!

If my Answer helped you solve your problem, please Accept it!

.

[Stephen23]

Also:

v = vertcat(x{:})

https://www.mathworks.com/matlabcentral/answers/1656435-tutorial-comma-separated-lists-and-how-to-use-them

[Seraphic]

@Stephen23 Thanks. Let me try it.