I think your problem is that the output from regexp is a cell array of cell arrays of strings (i.e. two levels of cell encapsulation), but you want it to be a cell array of strings. You can achieve that by adding the 'once' option to the call to regexp. Then you will get a cell array of strings that can be passed to str2double:

>> P = {'Rock_1', 'Rock_2', 'Rock_3'};  % Sample data
>> Rocks = regexp(P, '\d*', 'match');   % How you did it above
>> str2double(Rocks)

ans =

   NaN   NaN   NaN

>> Rocks = regexp(P, '\d*', 'match', 'once');  % With the 'once' option
>> str2double(Rocks)

ans =

     1     2     3

https://www.mathworks.com/matlabcentral/answers/437449-matlab-coder-giving-issue-with-textscan#answer_354189 X = "3.716,3.711,3.719,3.714,3.714,3.711,3.722,3.712,3.715,3.715,3.717,3.721,3.713,3.714,0.000"; str = X{1}; % character vector idx = str==','; idy = diff([true,idx,true]); idb = find(idy<0); ide = find(idy>0)-1; num = numel(idb); tmp = cell(num,1); for k = 1:num tmp{k} = str(idb(k):ide(k)); end vec = str2double(tmp)

X = str2double('newStr1') Y = str2doule('newStr2') You're trying to turn the literal character arrays 'newStr1' and 'newStr2' into numbers which, while they have an embedded numeric character aren't recognizable as numbers. You intended to use the variables instead-- X = str2double(newStr1) Y = str2doule(newStr2)

If the contents of the cell are _already_ numeric and the task is to convert from a cell array to a purely numeric array, then c1 = cell2mat(c);

The reason for the observed behavior is the stdio library used by Arduino. The code generated by str2double uses a function called sscanf. This function internally calls vfscanf function. vfscanf is available in three different versions. Out of these three versions, the default version does not implement scanning float variables. This is mentioned in the doc: "By default, all the conversions described above are available except the floating-point conversions and the width is limited to 255 characters. The float-point conversion will be available in the extended version provided by the library libscanf_flt.a. Also, in this case the width is not limited (exactly, it is limited to 65535 characters). To link a program against the extended version, use the following compiler flags in the link stage: -Wl,-u,vfscanf -lscanf_flt -lm " Refer the following doc link for more details: https://www.nongnu.org/avr-libc/user-manual/group__avr__stdio.html#ga67bae1ad3af79809fd770be392f90e21 To use compiler flags mentioned in the doc, you can follow the steps mentioned below: 1. Open config set 2. Go to "Code Generation" tab 3. In "Build configuration" drop down, select "Specify" 4. In C++ Liker, append the following: -Wl,-u,vfscanf -lscanf_flt -lm 5. Dont forget to add a space to the existing flags before appending the new flags. 6. Click apply, OK. 7. Run the model in external mode. Please note that using the extended version of this library will consume a lot of code space.