Convert negative values to zero in timetable

7 次查看（过去 30 天）
Kaiya Shealy
Kaiya Shealy 2022-6-9
评论： Peter Perkins 2022-6-13
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

请先登录，再回答此问题。

采纳的回答

Voss
Voss 2022-6-9
编辑：Voss 2022-6-9
Ran in:
% 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);
Time NOConc NO2Conc NOxConc ____________________ ________ ________ _________ 11-May-2022 20:36:01 0.56796 1.792 0.34045 12-May-2022 20:36:01 0.71024 -0.44977 2 13-May-2022 20:36:01 -0.98089 -0.96963 -1.1307 14-May-2022 20:36:01 -1.2461 1.1944 -0.14942 15-May-2022 20:36:01 0.32287 -0.67921 0.20059 16-May-2022 20:36:01 -0.98689 2.5576 1.0473 17-May-2022 20:36:01 -1.219 1.117 1.023 18-May-2022 20:36:01 0.82632 -1.0433 -0.033351
% replace negative values in NOConc column of Holly_NOx with 0:
Holly_NOx.NOConc(Holly_NOx.NOConc < 0) = 0;
disp(Holly_NOx);
Time NOConc NO2Conc NOxConc ____________________ _______ ________ _________ 11-May-2022 20:36:01 0.56796 1.792 0.34045 12-May-2022 20:36:01 0.71024 -0.44977 2 13-May-2022 20:36:01 0 -0.96963 -1.1307 14-May-2022 20:36:01 0 1.1944 -0.14942 15-May-2022 20:36:01 0.32287 -0.67921 0.20059 16-May-2022 20:36:01 0 2.5576 1.0473 17-May-2022 20:36:01 0 1.117 1.023 18-May-2022 20:36:01 0.82632 -1.0433 -0.033351
% or replace negative values in *any* column of Holly_NOx with 0:
Holly_NOx{:,:}(Holly_NOx{:,:} < 0) = 0;
disp(Holly_NOx);
Time NOConc NO2Conc NOxConc ____________________ _______ _______ _______ 11-May-2022 20:36:01 0.56796 1.792 0.34045 12-May-2022 20:36:01 0.71024 0 2 13-May-2022 20:36:01 0 0 0 14-May-2022 20:36:01 0 1.1944 0 15-May-2022 20:36:01 0.32287 0 0.20059 16-May-2022 20:36:01 0 2.5576 1.0473 17-May-2022 20:36:01 0 1.117 1.023 18-May-2022 20:36:01 0.82632 0 0
% another way to replace all negative values with 0:
Holly_NOx{:,:} = max(0,Holly_NOx{:,:});
disp(Holly_NOx);
Time NOConc NO2Conc NOxConc ____________________ _______ _______ _______ 11-May-2022 20:36:01 0.56796 1.792 0.34045 12-May-2022 20:36:01 0.71024 0 2 13-May-2022 20:36:01 0 0 0 14-May-2022 20:36:01 0 1.1944 0 15-May-2022 20:36:01 0.32287 0 0.20059 16-May-2022 20:36:01 0 2.5576 1.0473 17-May-2022 20:36:01 0 1.117 1.023 18-May-2022 20:36:01 0.82632 0 0
  7 个评论
显示 5更早的评论
Voss
Voss 2022-6-9
You're welcome! Any other questions, let me know.
Peter Perkins
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.

请先登录，再进行评论。

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Logical 的更多信息

标签

产品


版本

R2021b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by