Functions of Summary group are all, any, max, min, prod, range, and sum, which reduce a vector into a scalar (except range), thus the name of psummary(). Of course, other FUN can be passed-in, but functions like range() that returns a non-scalar vector result in unpredictable return. For arguments of different size, pmin() and pmax() make fractional recycling and issue warning, but psummary() error since as.data.frame() do not fractionally recycle.
psummary(...)# S3 method for garray
psummary(...)
# S3 method for default
psummary(...)
Usually in the form psummary(x, y, z, FUN=sum, na.rm=TRUE),
alternaitvely psummary(list(x, y, z), FUN=sum, na.rm=TRUE).