lapply returns NULL when using custom function

Question

I've experienced a similar problem more along the lines of being inefficient rather than than failing to function, it was solved here using lapply.

(Edited) I'm including working code with junk data this time that will throw the error back when run. The code below works as is, however I would like to replace the if (numruns ==... ) statements with the #'d lapply functions at the very end. The lapply using func_ign_time assigns NULL values. I'm also encountering some errors with the func_drop_time, but they may be related.

numruns = 3
pyro_1 <- as.numeric(c(100,70,50,2,3,4,60,160,260,360,503))
pyro_2 <- as.numeric(c(100,100,100,70,50,2,3,4,60,160,260,360,503))
pyro_3 <- as.numeric(c(100,100,70,50,2,3,4,60,160,260,360,503))
time_diff <- seq(1,100,1)

func_ign_time <- function(data, delay = 5, threshold = 5, time="time_diff"){
        diff_data <- diff(data[1:length(data)])
        flag <- 0
        for (i in 1:length(diff_data)){
                if (diff_data[i] > threshold && diff_data[i+1] > threshold && i > delay){
                        flag <- 1
                        time <- as.numeric(time_diff[i])
                        #print(paste0("Plug ignition time: ", time, " seconds"))
                        return (time)
                }
        }
}
func_drop_time <- function(data, threshold = -5, time="time_diff"){
        diff_data <- diff(data[1:length(data)])
        flag <- 0
        for (i in 1:length(diff_data)){
                if (diff_data[i] < threshold && flag == 0){
                        flag <- 1
                        time <- as.numeric(time_diff[i])
                        #print(paste0("Plug drop time: ", time, " seconds"))
                        return(time)
                }
        }
}

if (numruns == 3){
        time_ign_3 <- as.numeric(func_ign_time(pyro_3)-func_drop_time(pyro_3))
        time_ign_2 <- as.numeric(func_ign_time(pyro_2)-func_drop_time(pyro_2))
        time_ign_1 <- as.numeric(func_ign_time(pyro_1)-func_drop_time(pyro_1))
        print(paste(time_ign_1,time_ign_2,time_ign_3))
}
if (numruns == 2){
        time_ign_2 <- as.numeric(func_ign_time(pyro_2)-func_drop_time(pyro_2))
        time_ign_1 <- as.numeric(func_ign_time(pyro_1)-func_drop_time(pyro_1))
        print(paste(time_ign_1,time_ign_2))
}
if (numruns == 1){
        time_ign_1 <- as.numeric(func_ign_time(pyro_1)-func_drop_time(pyro_1))
        print(paste(time_ign_1))
}

#ign_names <- paste0("pyro_", seq_len(numruns))
#xx <- lapply(ign_names, function(x) (func_ign_time(x)))
#yy <- lapply(ign_names, function(x) (func_drop_time(x)))
#zz <- xx-yy

Answer 1

You're passing a char variable to func_ign_time(...), when it expects a vector (apparently). In other words, you're doing the equivalent of:

func_ign_time("pyro_1")

when you want

func_ign_time(pyro_1)

Try this instead:

lst <- list(pyro_1, pyro_2,pyro_3)
lapply(ign_names, func_ign_time)

Alternatively, try:

lapply(mget(ign_names), func_ign_time)