How to replace numbers (-999) for NaN in a dataset?

Hi,

I have a large dataset with variables containing -999. I want to change those numbers to NaN but it is not working...

 I2=find(Dataset==-999); Dataset(I2)=NaN;

...this is the error I get:

 Undefined operator '==' for input arguments of type 'dataset'.

Thank you for your help!

Answer 1

[Guillaume]

Note: datasets have been deprecated for a while. Consider using tables instead.

A dataset is a collection of variables. So you have to do your replacement per variable. e.g.

yourdataset.somevariable(yourdataset.somevariable == -999) = nan;
%same for all variables

Another option would be to use replacedata. For it to work you'll have to create an m file for a replacement function:

function X = datasetreplace(X)
   X(X == -999) = nan;
end

You can then do:

newdataset = replacedata(yourdataset, @datasetreplace)

[Robert]

Thank you so much for your help! I also appreciate your comment on dataset vs table, and to give me two options to proceed with my analysis.

[Robert]

Hi Guillaume,

Thank you for your help. I am wondering if I could follow with some questions on table? Or should I open another question? as this is a follow up to previous question...

It is OK with you, here is my question. I am trying to use the function grpstats as following:

 cd…
 load Example4Guillaume.mat

 Matrix1.Data(Matrix1.Data == -999)=nan;

 %creating submatrix and changing variables to nominal

 dsa1 = Matrix1(:,{'Location','Depth','Event','Data'});
 dsa1.Location = nominal(dsa1.Location);
 dsa1.Depth = nominal(dsa1.Depth);
 dsa1.Event = nominal(dsa1.Event);

 %Applying statarray

 statarray = grpstats(dsa1,'Depth');

I am trying to follow ‘hospital’ (https://www.mathworks.com/help/stats/grpstats.html) example but getting the following error:

 Error using dsgrpstats (line 266)
 Data variables must be numeric or logical.
 Error in grpstats (line 136)
    [varargout{1:nargout}] = 
 dsgrpstats(x,group,whichstats,varargin{:});

Not sure what I am doing wrong, any advice is welcome!

Attached is a very small example of my very large matrix (Example4Guillaume.mat).

Answer 2

[KSSV]

A = [-999 3 4 -999 4 5 -999] ;
B = A ;
B(B==-999) = NaN ;

Don't use find. It will be slow..use logical indexing..it will be quite fast.

[Robert]

Sorry, I was not clear, I need to do that to a 'dataset array'. That is because I get the error: Undefined operator '==' for input arguments of type 'dataset'.

[Robert]

Thank you so much KSSV, and sorry I was not clear the first time.