Error using string concatenation as input to ordinal( ) function

Question

Robyn Seery 2021-4-12

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/799896-error-using-string-concatenation-as-input-to-ordinal-function

评论： Robyn Seery 2021-4-12

rsrp.mat

Hi, I am trying to create dynamic legend titles, based on numeric input ranges (RSRP signal levels). Given input sorted_RSRP, I am adding a category column, to specify the signal ranges for plotting colour-coded map data.

To do this, I have attempted to combine string values in the ordinal( ) function so I can display the ranges (that would change for different data sets) in the legend. I get the following error:

Error using categorical (line 391)

CATEGORYNAMES must be a string array or cell array of character vectors containing non-blank category names.

Error in ordinal (line 148)

b = b@categorical(a,args{:},'Ordinal',true);

See code below:

% five data categories
p = 0:0.2:1;
breaks = quantile(rsrp,p)
% string concatenation to show numeric range values
a = num2str(breaks(1)) + " to " + num2str(breaks(2))
b = num2str(breaks(2)) + " to " + num2str(breaks(3))
c = num2str(breaks(3)) + " to " + num2str(breaks(4))
d = num2str(breaks(4)) + " to " + num2str(breaks(5))
e = "> " + num2str(breaks(5))
% categorise RSRP
catRSRP = ordinal(rsrp, {a,b,c,d,e}, [], breaks);
% I have also tried this, inputting string concatenation directly
% catRSRP = ordinal(data_sorted.RSRP, {num2str(breaks(1)) + " to " + num2str(breaks(2)), ... 
%     num2str(breaks(2)) + " to " + num2str(breaks(3)), ... 
%     num2str(breaks(3)) + " to " + num2str(breaks(4)), ... 
%     num2str(breaks(4)) + " to " + num2str(breaks(5)), ... 
%     "> " + num2str(breaks(5))}, [], breaks);

Not entirely sure what the error I am getting means, none of the a, b, c, d, e string variables are empty.

Any help would be greatly appreciated!

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the cyclist 2021-4-12

It would be helpful if you uploaded the data variable in a MAT file, so that we can see exactly what you are.

Robyn Seery 2021-4-12

@the cyclist Apologies, I completely forgot! I have edited the question and code, adding in the data I am using.

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Answer 1

Cris LaPierre 2021-4-12

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/799896-error-using-string-concatenation-as-input-to-ordinal-function#answer_673561

编辑：Cris LaPierre 2021-4-12

在 MATLAB Online 中打开

rsrp.mat

There is a warning at the top of the documentation page for ordinal

The nominal and ordinal array data types are not recommended. To represent ordered and unordered discrete, nonnumeric data, use the Categorical Arrays data type instead.

I think what you want to use is discretize to assign categories to the values based on what bin they would fall into. Use the syntax

[___] = discretize(___,'categorical',categoryNames)

load rsrp.mat
% five data categories
p = 0:0.2:1;
breaks = quantile(rsrp,p);
% string concatenation to show numeric range values
a = breaks(1) + " to " + breaks(2);
b = breaks(2) + " to " + breaks(3);
c = breaks(3) + " to " + breaks(4);
d = breaks(4) + " to " + breaks(5);
e = "> " + breaks(5);
% categorise RSRP
catRSRP = discretize(rsrp,breaks,'categorical',[a,b,c,d,e]);
catT = table(rsrp,catRSRP)
catT = 1153×2 table
rsrpcatRSRP________________

    -115    -115 to -103
    -114    -115 to -103
    -113    -115 to -103
    -113    -115 to -103
    -113    -115 to -103
    -113    -115 to -103
    -112    -115 to -103
    -112    -115 to -103
    -111    -115 to -103
    -111    -115 to -103
    -111    -115 to -103
    -111    -115 to -103
    -111    -115 to -103
    -111    -115 to -103
    -111    -115 to -103
    -110    -115 to -103