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

datasetnanreplace

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!

Best Answer

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)

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MATLAB: Grpstats for several variables

Have a look at the list of statistics that are accepted as character vectors. Note that 'median' is not one of the options.

https://www.mathworks.com/help/stats/grpstats.html#bthgdq6-whichstats

Instead, you'll need to use a function handle to list 'median' as a stat.

stat1 = grpstats(ds, {'Sodyum', 'AST'} , {'mean', @median});

That fixes any syntax issues. If problesm persist, please describe the problem in detail and share the result of the following line (assuming ds is a table which appears to be the case).

head(ds) % if ds is a table

MATLAB: Averaging sections of a vector

% Sample data
A=[1 3 -999 -999 -999 -999 4 9 8 -999 -999 -999];
% Replace the 'missing' -999 values with NaN
A(ismissing(A, -999)) = NaN;
% If you have a release that doesn't include ismissing, use ==
A(A == -999) = NaN;
% Take the mean, omitting NaN unless all the elements whose mean
% are being computed are NaN
M = mean(reshape(A, 3, []), 'omitnan')

Best Answer

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MATLAB: Averaging sections of a vector

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