Dear R-Help listers,
I am trying to estimate an proportional odds logistic regression model
(or ordered logistic regression) and then make predictions by
supplying a hypothetical x vector. However, somehow this does not
work. I guess I must have missed something here. I first used the polr
function in the MASS package, and I create a data frame and supply it
to the predict function (see below):
###############################################################
myologit <- polr(factor(warm) ~ yr89 + male + white + age + ed + prst,
data=ordwarm2, method=c("logistic"))
yr89 <- c(1)
male <- c(1)
white <- c(1)
age <- c(mean(ordwarm2$age))
ed <- c(mean(ordwarm2$ed))
prst <- c(mean(ordwarm2$prst))
prdata <- data.frame(yr89, male, white, age, ed, prst)
prdata$rankR <-predict(myologit,newdata=prdata,type="probs")
################################################################
I do not have any problem estimating the model, but when it comes to
the last time (predict), I got the following message:
Error in `$<-.data.frame`(`*tmp*`, "rankR", value = c(0.124294963178868, :
replacement has 4 rows, data has 1
Can anyone help me out with this error here? Thanks a lot!
Jun Xu, Phd
Assistant Professor
Department of Sociology
Ball State University
P.S.: below is the detailed output from R
################################################################
Call:
polr(formula = factor(warm) ~ yr89 + male + white + age + ed +
prst, data = ordwarm2, method = c("logistic"))
Coefficients:
Value Std. Error t value
yr89 0.523912 0.079899 6.557
male -0.733309 0.078483 -9.344
white -0.391140 0.118381 -3.304
age -0.021666 0.002469 -8.777
ed 0.067176 0.015975 4.205
prst 0.006072 0.003293 1.844
Intercepts:
Value Std. Error t value
1|2 -2.4654 0.2389 -10.3188
2|3 -0.6309 0.2333 -2.7042
3|4 1.2618 0.2340 5.3919
Residual Deviance: 5689.825
AIC: 5707.825
> # predictions for hypothetical data points
> # white male in year 89
> yr89 <- c(1)
> male <- c(1)
> white <- c(1)
> age <- c(mean(ordwarm2$age))
> ed <- c(mean(ordwarm2$ed))
> prst <- c(mean(ordwarm2$prst))
> prdata <- data.frame(yr89, male, white, age, ed, prst)
>
> prdata$rankR <-predict(myologit,newdata=prdata,type="probs")
Error in `$<-.data.frame`(`*tmp*`, "rankR", value = c(0.124294963178868, :
replacement has 4 rows, data has 1
>
> prdata
yr89 male white age ed prst
1 1 1 1 44.93546 12.21805 39.58526
###############################################################3
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