for (i in 1:100){data[i] <- full_data[i:(100000*i),]}

data <- list()
for (i in 1:100){data[[i]] <- full_data[((i-1)*10000+1):(i*10000),]}

data <- data.frame(1:1000000)

xtile <- function (x, n)
    {
        cuts <- quantile(x, probs = seq(0, 1, length = n + 1))
        cut(x, breaks = cuts, include.lowest = TRUE)
    }

group <- xtile(1:nrow(data), 100)
all(table(group)== 10000)

data.spl <- split(data, group)
data.spl[[2]]