使用 mapply 创建示例时出错

Question

我有一个这样的数据框：

df <- data.frame(size_upms = c(126, 123, 148),
             electric_mean = c(0.716756756756757,0.647859922178988, 0.726313694267516),
             gas_mean = c(0.273513513513513,0.322679266259033, 0.259554140127389),
             firewood_mean = c(0, 0.00111172873818788,0.00179140127388535))

# df
#  size_upms electric_mean  gas_mean firewood_mean
#1       126     0.7167568 0.2735135   0.000000000
#2       123     0.6478599 0.3226793   0.001111729
#3       148     0.7263137 0.2595541   0.001791401

我想使用 mapply 为每一行使用参数获取样本

l <- mapply(sample,c("electric","gas","firewood"),df$size_upms,TRUE,
            c(df$electric_mean,df$gas_mean,df$firewood_mean))

但是我得到这个错误：

#Error in sample.int(length(x), size, replace, prob) : 
#  too few positive probabilities

但是，如果我将示例函数应用于每一行，它就会起作用：

sample(c("electric","gas","firewood"),df$size_upms[1],TRUE,
   c(df$electric_mean[1],df$gas_mean[1],df$firewood_mean[1]))[1:5]
#[1] "gas"      "electric" "electric" "gas"      "electric"
sample(c("electric","gas","firewood"),df$size_upms[2],TRUE,
   c(df$electric_mean[2],df$gas_mean[1],df$firewood_mean[2]))[1:5]
#[1] "electric" "gas"      "gas"      "gas"      "electric"
sample(c("electric","gas","firewood"),df$size_upms[3],TRUE,
   c(df$electric_mean[3],df$gas_mean[3],df$firewood_mean[1]))[1:5]
#[1] "electric" "electric" "gas"      "electric" "electric"

但是我想使用 mapply 因为我想将它应用到一个大数据帧

我做错了什么？

Answer 1

因为是按行，所以用apply或lapply更容易。 mapply 或其他 apply 解决方案

之间的性能不会有太大差异

lapply(seq_len(nrow(df)), function(i) 
    sample(c("electric","gas","firewood"), df$size_upms[i], TRUE, 
    unlist(c(df$electric_mean[i],df$gas_mean[i],df$firewood_mean[i]))))

OP的解决方案中的错误是连接过程。在这里，我们将参数作为数据集中的单独列传递，然后在匿名函数调用中进行连接。这将确保对于每个步骤，都会选择列中的相应行元素。

Map(function(x,y, u, w) sample(c("electric","gas","firewood"), x, 
     TRUE, c(y, u, w)), df$size_upms, df$electric_mean, df$gas_mean, df$firewood_mean)

或者正如@thelatemail 评论的那样，我们可以通过使用 do.call

来避免一些输入

do.call(Map, c( function(x,y, u, w) 
    sample(c("electric","gas","firewood"), x, TRUE, c(y,u,w)), unname(df)))

使用 mapply 创建示例时出错

Error creating samples with mapply

r

mapply