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rpsych

R psych, cohen.d error Error in `.rowNamesDF<-`(x, value = value) : invalid 'row.names' length

I get the below error when trying to compute effect size using cohen.d function in psych. Please see example data below. 

library(psych)
x <- c(1, 2, 3, 4, 5, 6, 7, 8)
y <- c(1, 1, 1, 1, 2, 2, 2, 2)
xy <- data.frame(x,y)
names(xy) <- c("x", "group")
CohensD <- cohen.d(xy, "group", alpha=.05)

Error in .rowNamesDF<-(x, value = value) : invalid 'row.names' length

Solution

  • Probably there is a bug as it works fine in 1.8.12, also it generates the same error with 

    cohen.d(sat.act[1:8, c('education','gender')], "gender")

    but not with 

    cohen.d(sat.act[1:8, c('education','gender','age')], "gender")

    So, should work fine with a data frame has more than two columns 

    x <- c(1, 2, 3, 4, 5, 6, 7, 8)
y <- c(1, 1, 1, 1, 2, 2, 2, 2)
xy <- data.frame(x=x, group=y, z=rnorm(8))
cohen.d(xy, "group")

Call: cohen.d(x = xy, group = "group")
Cohen d statistic of difference between two means
  lower effect upper
x  0.53   3.58  6.60
z -0.71   0.88  2.37

Multivariate (Mahalanobis) distance between groups
[1] 3.6
r equivalent of difference between two means
   x    z 
0.87 0.40