如何获取最后一个非NA列的值 [英] How to get value of last non-NA column

问题描述

有点难以解释，但是我有一个数据框，其值看起来像一个阶梯-对于每个日期，都有不同的列，其中某些日期具有NA.我想创建一个新列，其中包含最后一个非NA列的值.

A bit difficult to explain, but I have a dataframe with values that look like a staircase - for every date, there are different columns that have NA for some dates. I want to create a new column that has the last non-NA column value in it.

希望这个例子更有意义:

Hopefuly it makes more sense with this example:

示例数据框:

test <- data.frame("date" = c(as.Date("2020-01-01"), as.Date("2020-01-02"), as.Date("2020-01-03")),
                   "a" = c(4, 3, 4),
                   "b" = c(NA, 2, 1),
                   "c" = c(NA, NA, 5))

所需的输出:

date............val
2020-01-01...... 4
2020-01-02...... 2
2020-01-03...... 5

我也不想做类似日期的行号和那列号+ 1的事情，但是如果那是唯一的方法，那就那样.谢谢！

I'd also prefer not to do something like take the row number of the date and take that column number + 1, but if that's the only way to do it, that's that. Thanks!

推荐答案

您可以将 max.col 与 ties.method 设置为"last"一起使用；以获得每行中的最后一个非NA值.

You can use max.col with ties.method set as "last" to get last non-NA value in each row.

test$val <- test[cbind(1:nrow(test), max.col(!is.na(test), ties.method = 'last'))]
test

#        date a  b  c val
#1 2020-01-01 4 NA NA   4
#2 2020-01-02 3  2 NA   2
#3 2020-01-03 4  1  5   5

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