Convert negative values to zero in timetable
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I have a timetable that has 4 columns that are Date, NOConc, NO2Conc, NOxConc. I want to convert any negative numbers in the NOConc column to zero. The S function pulls the data from the larger timetable, TN_1, for a specific time range that I'm looking at (in this case 5/11/2022 - 5/18/2022) and makes the new timetable labeled Holly_NOx, with a variable amount of rows depending on the given date range. This code is the closest I've gotten, but it gives me the error "A variable index must be a real positive integer." I've seen some people say matlab wont allow indexing of negative integers, which would make what I'm trying to do impossible. Thanks!!
S = timerange('5/11/2022' , '5/18/2022', 'days');
Holly_NOx = TN_1(S,:);
if Holly_NOx.(Holly_NOx.NO2Conc) > 0
Holly_NOx.(Holly_NOx.NO2Conc) = 0;
end
采纳的回答
% a timetable with 3 data columns:
Holly_NOx = timetable(datetime(now+(-29:-22),'ConvertFrom','datenum').', ...
randn(8,1),randn(8,1),randn(8,1), ...
'VariableNames',{'NOConc' 'NO2Conc' 'NOxConc'});
disp(Holly_NOx);
% replace negative values in NOConc column of Holly_NOx with 0:
Holly_NOx.NOConc(Holly_NOx.NOConc < 0) = 0;
disp(Holly_NOx);
% or replace negative values in *any* column of Holly_NOx with 0:
Holly_NOx{:,:}(Holly_NOx{:,:} < 0) = 0;
disp(Holly_NOx);
% another way to replace all negative values with 0:
Holly_NOx{:,:} = max(0,Holly_NOx{:,:});
disp(Holly_NOx);
7 个评论
Voss
2022-6-9
This works!! Thank you very much!
Kaiya Shealy
2022-6-9
Voss
2022-6-9
The code here is generating a timetable with random data, and then showing a few ways to replace negative data in the table - either in one column or all columns. You should pick the command you want to use and apply it to your table, i.e., don't create the random data each time, which was only for demonstration.
Kaiya Shealy
2022-6-9
Voss
2022-6-9
You're welcome! Any other questions, let me know.
Peter Perkins
2022-6-13
Voss gets points for using braces on a table to modify the values. For more context on that, see the Arithmetic on Table Variables section of this example from the doc.
Another way to do this would be
Holly_NOx = varfun(@(x)max(x,0),Holly_NOx);
For large timetables, that's likely to be faster.
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