[R] Adjusting length of series

[David Winsemius]

On Jun 30, 2012, at 6:04 PM, Lekgatlhamang, lexi Setlhare wrote:

> Hi
> I have a follow up question, relating to subsetting to list items.  
> After using the list and min(sapply()) method to adjust the length  
> of the variables, I specify a dynamic regression equation using the  
> variables in the list. My list looks like this:
> Dcr<-  
> list 
> (Dcre1 
> = 
> DCred1 
> ,Dcre2 
> =DCred2,Dcre3=DCred3,Dbobc1=DBoBC1,Dbobc2=DBoBC2,Dbobc3=DBoBC3,...)

This should ahve been done like this:

Dcr<- data.frame(Dcre1=DCred1, Dcre2=DCred2, Dcre3=DCred3,  
Dbobc1=DBoBC1, Dbobc2=DBoBC2, Dbobc3=DBoBC3)

> By specifying the list items with names, I thought I could end by  
> referencing them (or subsetting the list) as, eg., Dcr$Dcre1 and get  
> DCred1, Dcr$Dbobc1 and get DBoBC1, etc so that the explanatory  
> variables of the equation can be easily associated with their  
> respective original names. This way, I would avoid specifying the  
> list as Dcr<-list(Dcr1, Dcr2, Dcr, 3..., Dcr15) and then subsetting  
> the list using Dcr[[1]][1:29], Dcr[[[2]][1:29], ..., Dcr[[15]][1:29]  
> because the list has many variables (15) and referencing the  
> variables with numbers makes them lose their original names.
> When I specify the list as Dcr<- list(Dcr1, Dcr2, ..., Dcr15), then  
> the regression equation specified as:
> # Regression
> regCred<- lm(Dcr[[1]][1:29]~Dcr[[2]][1:29]+Dcr[[3]][1:29]+Dcr[[4]] 
> [1:29]+Dcr[[5]][1:29]+Dcr[[6]][1:29]+...)

And the you could have done

> regCred<- lm(Dcre1 ~ . , data=Dcr [ , 1:29] )

(Leaving out the , ...)


> runs without problems - the results are shown here below:
> Call:
> lm(formula = Dcr[[1]][1:29] ~ Dcr[[2]][1:29] + Dcr[[3]][1:29] +
> Dcr[[4]][1:29] + Dcr[[5]][1:29] + Dcr[[6]][1:29])
> Residuals:
> Min      1Q  Median      3Q     Max
> -86.293 -33.586  -9.969  40.147 117.965
> Coefficients:
> Estimate Std. Error t value Pr(>|t|)
> (Intercept)    81.02064   13.28632   6.098 3.21e-06 ***
> Dcr[[2]][1:29] -0.97407    0.11081  -8.791 8.20e-09 ***
> Dcr[[3]][1:29] -0.27950    0.05899  -4.738 8.95e-05 ***
> Dcr[[4]][1:29] -0.07961    0.04856  -1.639    0.115
> Dcr[[5]][1:29] -0.07180    0.05515  -1.302    0.206
> Dcr[[6]][1:29] -0.01562    0.02086  -0.749    0.462
>
> But when I specify the list with names as shown above, then the  
> equation does not run - as shown by the following error message
>> # Regression
>> regCred<- lm(Dcr[[1]][1:29]~Dcr[[2]][1:29]+Dcr[[3]][1:29]+Dcr[[4]] 
>> [1:29]+
> + Dcr[[5]][1:29]+Dcr$Dbobc3)
> Error in model.frame.default(formula = Dcr[[1]][1:29] ~ Dcr[[2]] 
> [1:29] +  :
> variable lengths differ (found for 'Dcr$Dbobc3')
>> Dcr[[5]][1:29]+Dcr$Dbobc3[1:29])
> Error: unexpected ')' in "Dcr[[5]][1:29]+Dcr$Dbobc3[1:29])"
>
> NB: In the equation with error message, only the last term is  
> specified by referencing its name (ie., Dcr$Dbobc3[1:29]. Also note  
> that the error occurs whether I append '[1:29]' to Dcr$Dbobc or not.
> How do I resolve this?

You should have offered str(Dcr)


> Thanks. Lexi
>
> NB: I tried typing the above in the same email Petr used to reply  
> me, but the email could not be delivered due to size problems
> 	[[alternative HTML version deleted]]
>
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David Winsemius, MD
West Hartford, CT