Hi there,

Iam working through code for Rstudio that was provided from R cookbook and should run smoothly butI am continually receiving error messages. The first issue I am experiencing is occurring during the set up for summarySE function. The code is as follows:

# Summarizes data.

# Gives count, mean, standard deviation, standard error of the mean,

# and confidence interval (default 95%).

# data: a data frame.

# measurevar: the name of a column that contains the variable to be

# summarized

# groupvars: a vector containing names of columns that contain

# grouping variables

# na.rm: a boolean that indicates whether to ignore NA's

# conf.interval: the percent range of the confidence interval

# (default is 95%)

summarySE <- function(data=NULL, measurevar, groupvars=NULL, na.rm=FALSE,

conf.interval=.95, .drop=TRUE) {

require(plyr) }

# New version of length which can handle NA's: if na.rm==T, don't

# count them

length2 <- function (x, na.rm=FALSE) {

if (na.rm) sum(!is.na(x))

elselength(x)

}

# This does the summary. For each group's data frame, return a

# vector with N, mean, and sd

datac <- ddply(data, groupvars, .drop=.drop,

.fun = function(xx, col) {

c(N= length2(xx[[col]], na.rm=na.rm),

mean = mean(xx[[col]], na.rm=na.rm),

sd= sd(xx[[col]], na.rm=na.rm)

)

},

measurevar

)

# Rename the "mean" column

datac <- rename(datac, c("mean" = measurevar))

datac$se <- datac$sd / sqrt(datac$N)# Calculate standard error of the mean

# Confidence interval multiplier for standard error

# Calculate t-statistic for confidence interval:

# e.g., if conf.interval is .95, use .975 (above/below), and use df=N-1

ciMult <- qt(conf.interval/2 + .5, datac$N-1)

datac$ci <- datac$se * ciMult

return(datac)

}

The error I receive is: Error in if (empty(.data)) return(.data) : missing value where TRUE/FALSE needed 

I would really appreciate your help with this. I can send through the csv file I am working with if that helps.

Kind regards,

Gabrielle