MATLAB: How to code Categorical Variables in NARX neural network data input

categorical variablesMATLABnarxneural networkstime series

I am working to predict electricity demand (load) and I am having many categorical variables as inputs to a Neural Network Time Series NARX app (eg: months (12 categories spelled out January -December), days (seven categories: 1 – 7), and Hours in each day (1 thru 24). When I load my excel data table to assign "Inputs" as my variables, the Matlab is not able to read and display my categorical variable "Months" because the values are spelled out January thru December. Should I write a simple line code such as below, or is there a different way to flag those variables as Categorical for NARX neural networks? I prefer not to convert Months into 1-12 as Matlab will assume some scale (Month 12 is higher than Month 6, etc). Thank you in advance!
T.HE = categorical(T.HE); T.MONTH = categorical(T.MONTH);T.WEEKDAY = categorical(T.WEEKDAY);

Best Answer

T.MONTH_C = categorical(T.MONTH, {'January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December'}, 'ordinal', false);
T.HE_C = categorical(T.HOUR, 1:24, {'01:00', '02:00', '03:00', '04:00', ....... '24:00'}, 'ordinal', false);
T.WEEKDAY_C = categorical(T.WEEKDAY, 1:7, {'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday'}, 'ordinal', false);
I prefer not to convert Months into 1-12 as Matlab will assume some scale (Month 12 is higher than Month 6, etc)
I do not know what part of the world you live in, but in the part of the world that I live in, the electrical demands between adjacent calendar months are strongly correlated. The relationship between the demands for January and February are much stronger than the relationship between the demands between January and June.
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