for loop for creating multiple data frames and assigning values

Question

I would like to create multiple data frames and assign them based on years. I have seen other posts but I couldn't duplicate it for my case. For example,

a <- c(1,2,3,4)
b <- c('kk','km','ll','k3')
time <- (2001,2001,2002,2003)
df <- data.frame(a,b,time)
myvalues <- c(2001,2002,2003)
for (i in 1:3) 
{ y[[i]]<- df[df$time=myvalues[[i]],}

I would like to create three dataframes y1, y2, y3 for years 2001, 2002 and 2003. Any suggestions how do using a for loop?

You have three problems - you need to initialize the list before the loop, y = list(), use == not = for testing equality, and you have unmatched brackets in your loop, {y[[i]] <- df[df$time == myvalues[i],]}. However instead of the for loop you can just do y = split(df, df$time) — Gregor Thomas
– Gregor Thomas, Commented Jun 15, 2017 at 19:11
See also how to make a list of data frames (possible dupe?). — Gregor Thomas
– Gregor Thomas, Commented Jun 15, 2017 at 19:12

psychOle · Accepted Answer · 2018-10-01 08:35:08Z

9

The assign() function is made for this. See ?assign() for syntax.

a <- c(1,2,3,4)
b <- c("kk","km","ll","k3")
time <- c(2001,2001,2002,2003)
df <- data.frame(a,b,time)
myvalues <- c(2001,2002,2003)

for (i in 1:3) {
  assign(paste0("y",i), df[df$time==myvalues[i],])
  }

See here for more ways to achieve this.

edited Oct 1, 2018 at 8:35

answered Jun 15, 2017 at 19:10

psychOle

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