How to prevent pmax/pmin from taking non-numerical values into consideration?

I am using pmax and pmin to extract the max and min values from each row. I have some values that are statistically not significant and these values are surrounded by <>. For some reason, pmax and pmin still take into consideration these values and then I cannot calculate the difference between values that are significant. Below is an example:

I want the !xx! values not included when I do the following:

DF1 = data.frame(ID=c("A","B","C","D","E"), 
                 Var1=c("1","20","!20!","NA","!10!"), 
                 Var2=c("!5!","NA","10","NA","NA"), 
                 Var3=c("NA","NA","NA","30","NA"), 
                 Var4=c("10","NA","NA","NA","NA"),
                 Var5=c("NA","!50!","20","NA","NA"))

DF1$max <- pmax(DF1$Var1,DF1$Var2,DF1$Var3,DF1$Var4,na.rm = TRUE)
DF1$min <- pmin(DF1$Var1,DF1$Var2,DF1$Var3,DF1$Var4,na.rm = TRUE)

This leads to me getting the following:

When the following is what I want:

How do I prevent the !xx! values from being taken up by pmax and pmin? I appreciate any help!

>Solution :

Assuming your "NA" is really NA (not a string literal):

DF1[-1] <- lapply(DF1[-1], function(z) replace(z, z=="NA", NA))

we can do this:

do.call(pmax, c(lapply(DF1[-1], function(z) replace(z, grepl("!", z), NA)), list(na.rm = TRUE)))
# [1] "10" "20" "20" "30" NA  

results stored with:

DF1$max <- do.call(pmax, c(lapply(DF1[-1], function(z) replace(z, grepl("!", z), NA)), list(na.rm = TRUE)))
DF1$min <- do.call(pmin, c(lapply(DF1[-1], function(z) replace(z, grepl("!", z), NA)), list(na.rm = TRUE)))
DF1
#   ID Var1 Var2 Var3 Var4 Var5  max  min
# 1  A    1  !5! <NA>   10 <NA>   10    1
# 2  B   20 <NA> <NA> <NA> !50!   20   20
# 3  C !20!   10 <NA> <NA>   20   20   10
# 4  D <NA> <NA>   30 <NA> <NA>   30   30
# 5  E !10! <NA> <NA> <NA> <NA> <NA> <NA>

Note that we also need to add na.rm=FALSE.