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Box Plots for Vectors of Varying Length

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Nuria Andreu
Nuria Andreu on 21 Jun 2021
Commented: Nuria Andreu on 23 Jun 2021
Hello! I have 3 data sets named DailyTMAX_1, DailyTMAX_2, and DailyTMAX_3. Each one of them have maximum temperature data. DailyTMAX_1 from years 1931-1960, DailyTMAX_2 from 1961-1990, and DailyTMAX_3 from 1991 to 2020.
The three of them have varying lenghts. DailyTMAX_1 is 10321, DailyTMAX_2 is 11243 and DailyTMAX_3 is 10792.
I want to create a boxplot but every time I run it I get this message:
"Error: File: ClimateDataProcessor.m Line: 107 Column: 14
Invalid text character. Check for unsupported symbol, invisible character, or pasting of non-ASCII characters."
Line 107 Column 14 corresponds to g1 on the attached code
x = [DailyTMAX_1; DailyTMAX_2; DailyTMAX_3];
g1 = repmat({1931-1960},10321,1);
g2 = repmat({1961-1990},11243,1);
g3 = repmat({1991-2020},10792,1);
g = [g1; g2; g3];
boxplot(x,g)
Hope anyone can help me with this
Thank you!

Accepted Answer

Joel Lynch
Joel Lynch on 22 Jun 2021
Edited: Joel Lynch on 22 Jun 2021
The proximate error is that the symbols around the year-range string
1931-1960
are not apostrophes, so MATLAB doesn't know what to do with them. They should appear in pink:
'1931-1960'
But that is a moot point, because you don't need to use the "g" argument in boxplot for this problem. The g argument is used to group heterogenous elements of each column in x together in seperate boxplots. You're data is already homogenous in each vector, so you can just pass three columns in x to get three boxplots. The trick is to handle their unequal lengths, which you can do by filling a just-large-enough NaN matrix x. The extra elements in each column are ignored by boxplot.
N = max( [ numel(DailyTMAX_1), numel(DailyTMAX_2), numel(DailyTMAX_3) ] ); % Longest length
x = NaN(N,3); % 3 columns large enough to fit longest vector
x(1:numel(DailyTMAX_1),1) = DailyTMAX_1;
x(1:numel(DailyTMAX_2),2) = DailyTMAX_2;
x(1:numel(DailyTMAX_3),3) = DailyTMAX_3;
boxplot(x);
You can greatly simplify this by storing "DailyTMAX_X" vectors natively in a NaN-padded x matrix.
Note: this won't add the year-labels, you can do that manually by:
set( gca, 'XTickLabel', {'1931-1960', '1961-1990', '1991-2020'} );
  4 Comments
Nuria Andreu
Nuria Andreu on 23 Jun 2021
Hi Joel thank you so much! It worked. The problem was the apostrophe. I didn't see it until you mentioned it.

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