如何限制sapply函数中的计算？ [英] How to limit the calculation in a sapply function?

问题描述

几个星期前，我在根据另一个数据帧中的信息来计算系数时遇到问题-到最后一个问题的链接。
@PoGibas提供的解决方案效果很好，但是，我必须将计算限制为在定义的时间之后，数据帧 A 中的下一个10个值。每一行。请你帮助我好吗？
我的代码看起来像@PoGibas建议的：

Several weeks ago I had a problem with calculating a coefficient in dependence to information from another data frame - the link to the last question. The solution provided by @PoGibas worked very well, however, I have to limit the calculation to only the 10 next values from data frame A after a defined time in each row. Could you please help me? My code looks as @PoGibas proposed:

sapply(1:length(time), function(x) sum(df1[x, which(foo >= time[x])]))

推荐答案

以下代码修改了您现有的代码，因此只有前10个条目（如果存在）才被选择和求和。如果条目少于10个，则需要 na.rm = TRUE 。在这种情况下，R自动使用 NA 填充空索引。

The following code modifies your existing code so that only the first 10 entries are selected and summed, if they exist. The na.rm = TRUE is needed for cases where there may be fewer than 10 entries. In such cases, R automatically fills the "empty" indices with NA.

sapply(1:length(time), function(x) sum(df1[x, which(foo >= time[x])][1:10], na.rm = TRUE))

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