[R] Problems with subset, droplevels and lm: variable lengths differ

[Joshua Wiley]

Hi Michael,

Just a silly error, it should be:

mod1 <- lm(cbind(Cu, Fe, K, Mg, Mn, P, Zn) ~ litho + forest + weather,
data=Oslo)

quoted you get a 1 x 7 character matrix you are trying to regress on.

Cheers,

Josh

On Mon, Apr 16, 2012 at 10:43 AM, Michael Friendly <friendly at yorku.ca> wrote:
> [Env:  R 2.14.2 / Win Xp]
>
> In the script below, I want to select some variables from
> rrcov::OsloTransect, delete cases with
> any missing data, and subset the data frame Oslo to remove cases for two
> levels of the
> factor litho that occur with low frequency.
>
> The checks I run on my new data frame Oslo look OK, but I when I try to fit
> a multivariate
> linear model with lm(), I am getting an error: variable lengths differ
> (found for 'litho').
> How can I fix this?
>
>> data(OsloTransect, package="rrcov")
>> # keep a subset of variables & rename some variables
>> Oslo <-OsloTransect[c("X.ID", "XCOO", "YCOO", "X.FOREST", "X.WEATHER",
>> "X.FLITHO", "ALT")]
>> colnames(Oslo) <- c("site", "XC", "YC", "forest", "weather", "litho",
>> "altitude")
>> Oslo <- cbind(Oslo, OsloTransect[,c("Cu", "Fe", "K", "Mg", "Mn", "P",
>> "Zn")])
>> # make site a factor
>> Oslo[,"site"] <- factor(Oslo[,"site"])
>>
>> # log transform the chemical elements
>> Oslo[,8:14] <- log(Oslo[,8:14])
>>
>> # delete cases with missing data
>> Oslo <- Oslo[complete.cases(Oslo),]
>> nrow(Oslo)
> [1] 350
>>
>> # delete low frequency litho=="GNEID_O" | "MICSH"
>> Oslo <- subset(Oslo, !litho %in% c("GNEID_O", "MICSH"), drop=TRUE)
>> nrow(Oslo)
> [1] 332
>> Oslo<- droplevels(Oslo)
>> table(Oslo$litho)
>
>  CAMSED GNEIS_O GNEIS_R    MAGM
>     98      89      32     113
>> nrow(Oslo)
> [1] 332
>> mod1 <- lm(cbind("Cu", "Fe", "K", "Mg", "Mn", "P", "Zn") ~ litho + forest
>> + weather, data=Oslo)
> Error in model.frame.default(formula = cbind("Cu", "Fe", "K", "Mg", "Mn",  :
>  variable lengths differ (found for 'litho')
>>
>
>
>
> --
> Michael Friendly     Email: friendly AT yorku DOT ca
> Professor, Psychology Dept.
> York University      Voice: 416 736-5115 x66249 Fax: 416 736-5814
> 4700 Keele Street    Web:   http://www.datavis.ca
> Toronto, ONT  M3J 1P3 CANADA
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.



-- 
Joshua Wiley
Ph.D. Student, Health Psychology
Programmer Analyst II, Statistical Consulting Group
University of California, Los Angeles
https://joshuawiley.com/