# How do I put days of the week into a multiple regression model?

1. ## How do I put days of the week into a multiple regression model?

I am building a multiple linear regression model to predict peak power demant
using maximum daily temerature (in degrees) and the day of the week as
independent variables. I am unsure how to code the days of the week in order
to get the result I want. (when I use the days - the regression add-in tool
states that I'm not using the correct type of data, its non-numeric). I
believe this model will have 7 seperate independent variables, but am unsure
on how to get there.

2. ## Re: How do I put days of the week into a multiple regression model?

On Sun, 5 Feb 2006 15:43:26 -0800, "Paula" <Paula@discussions.microsoft.com>
wrote:

>I am building a multiple linear regression model to predict peak power demant
>using maximum daily temerature (in degrees) and the day of the week as
>independent variables. I am unsure how to code the days of the week in order
>to get the result I want. (when I use the days - the regression add-in tool
>states that I'm not using the correct type of data, its non-numeric). I
>believe this model will have 7 seperate independent variables, but am unsure
>on how to get there.

Sunday = 1
Monday = 2

etc.

or, if you have actual dates, use the WEEKDAY worksheet function.

--ron

3. If I understand correctly coding Monday to 1, Tuesday to 2 etc will create one variable for days of the week and assume that tuesday is double monday! I don't think this is what you want.

You need to create 7 variables
One for each day eg 1 if monday 0 if not as one variable, 1 if tuesday 0 if not etc. Although arguably you could get way with six variables as if it is not mon-sat it has to be sunday!
day mon tue wed thu fri sat sun
Monday,1,0,0,0,0,0,0
Tuesday,0,1,0,0,0,0,0
Wednesday,0,0,1,0,0,0,0
Thursday,0,0,0,1,0,0,0
Friday,0,0,0,0,1,0,0
Saturday,0,0,0,0,0,1,0
Sunday,0,0,0,0,0,0,1

Regards
Dav

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