Compute standard errors (within-subjects)

seWithin is used to compute the standard error(s) for one or more variables, for one or more groups in a dataframe, handling within-subjects variables by removing inter-subject variability

seWithin(data = NULL, measurevar, betweenvars = NULL, withinvars = NULL,
idvar = NULL, na.rm = TRUE, conf.interval = 0.95, shownormed = FALSE)

Arguments

data	a dataframe
measurevar	the name(s) of column(s) that contain the variable to be summariezed
betweenvars	a vector containing names of columns that are between-subjects variables
withinvars	a vector containing names of columns that are within-subjects variables
idvar	the name of the column that identifies each subject
na.rm	boolean that indicates whether to ignore NA's
conf.interval	confidence interval range
shownormed	whether to show noramlized results

Value

A data.table

Note

Code adapted from R cookbook (see references).

References

http://www.cookbook-r.com/Graphs/Plotting_means_and_error_bars_(ggplot2)/

Author

Hause Lin

Examples

result <- seWithin(data = ChickWeight, measurevar = "weight",
betweenvars = "Diet", withinvars = "Time", idvar = "Chick")
#> Automatically converting the following non-factors to factors: Time
#> Joining, by = c("Chick", "Diet")
#> Joining, by = c("Diet", "Time", "N")
#> Factors have been converted to characters.
#> Confidence intervals: 0.95
#> 

# multiple outcome variables
ChickWeight2 <- ChickWeight
ChickWeight2$weight2 <- ChickWeight2$weight * 100 # create a new outcome variable
result <- seWithin(data = ChickWeight2, measurevar = c("weight", "weight2"),
betweenvars = "Diet", withinvars = "Time", idvar = "Chick")
#> Automatically converting the following non-factors to factors: Time
#> Joining, by = c("Chick", "Diet")
#> Joining, by = c("Diet", "Time", "N")
#> Factors have been converted to characters.
#> Confidence intervals: 0.95
#> 
#> Joining, by = c("Chick", "Diet")
#> Joining, by = c("Diet", "Time", "N")
#> Factors have been converted to characters.
#> Confidence intervals: 0.95
#>