[英]apply a function to some elements of a nested lists in R
我希望仅将函数应用于嵌套列表的某些元素
l <- list()
l$a$forecast <- rnorm(3)
l$a$model <- "arima"
l$b$forecast <- rnorm(3)
l$b$model <- "prophet"
所需的输出将是这样的:将 sum 函数应用于列表的 $forecast 元素
fcst <- c(sum(l$a$forecast),sum(l$b$forecast))
mdl <- c(l$a$model,l$b$model)
df <- data.frame(fcst,mdl)
我试过这样的事情:
df <- lapply(l$forecast, function(x) sum(x))
df <- do.call(rbind, Map(cbind, sku = names(df)))
do.call(
rbind,
lapply(
l,
function(x) list(fcst = sum(x$forecast), model = x$model)
)
)
由于您知道返回对象的确切尺寸,因此您可以在这种情况下使用vapply
来提高性能:
vapply(
l,
FUN = function(x) list(fcst = sum(x$forecast), model = x$model),
FUN.VALUE = list(fcst = numeric(1), model = character(1))
)
但是,生成的对象可能很难处理。
在rrapply
使用rrapply()
另一种方法结合 dplyr 的bind_rows()
。 这也扩展到包含更深嵌套级别的列表。
rrapply::rrapply(l, condition = function(x, .xname) .xname == "forecast", f = sum) %>%
dplyr::bind_rows()
#> # A tibble: 2 x 2
#> forecast model
#> <dbl> <chr>
#> 1 -1.28 arima
#> 2 1.10 prophet
数据
set.seed(1)
l <- list(
a = list(forecast = rnorm(3), model = "arima"),
b = list(forecast = rnorm(3), model = "prophet")
)
您可以使用对象来获取letters
,然后在循环中使用其输出:
n = 2 #number of lists you have
sumfore = model = vector()
for(i in letters[seq(1,n,1)]){
sumfore[i] = sum(l[[i]]$forecast)
model[i] =l[[i]]$model}
newdf = data.frame(sumfore, model)
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