calculating drop1 R^2s
Dear Michael, How about the following? y <- model.response(model.frame(base.mod)) TSS <- sum((y - mean(y))^2) 1 - drop.mod$RSS/TSS I hope this helps, John
-----Original Message----- From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On
Behalf Of Michael Friendly Sent: April-02-09 5:39 PM To: R-Help Subject: [R] calculating drop1 R^2s This is probably simple, but I just can't see it... I want to calculate the R^2s for a series of linear models where each term is dropped in turn. I can get the RSS from drop1(), and the r.squared from summary() for a given model, but don't know how to use the result of drop1() to get the r.squared for each model with one term
dropped.
Working example:
library(vcd) # for Baseball
library(car) # for vif/recode
data(Baseball)
# sal87 appears as a factor because missing is coded as '.' rather than NA
Baseball$sal87 <- as.numeric(recode(Baseball$sal87, "'.'=NA"))
Baseball$logsal <- log(Baseball$sal87)
base.mod <- lm(logsal ~ years+atbat+hits+homeruns+runs+rbi+walks,
data=Baseball)
vif(base.mod)
(drop.mod <- drop1(base.mod))
Single term deletions
Model:
logsal ~ years + atbat + hits + homeruns + runs + rbi + walks
Df Sum of Sq RSS AIC
<none> 124.612 -180.447
years 1 0.010 124.622 -182.426
atbat 1 0.570 125.182 -181.247
hits 1 0.256 124.869 -181.906
homeruns 1 0.001 124.613 -182.445
runs 1 0.691 125.303 -180.993
rbi 1 0.091 124.704 -182.254
walks 1 0.408 125.020 -181.588
--
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 http://www.math.yorku.ca/SCS/friendly.html
Toronto, ONT M3J 1P3 CANADA
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