如何用R中的NA替换特定行和列中的某些值?

在我的数据框中，我想用NA替换某些空白单元格和具有值的单元格.但是我要替换为NA的单元格与单元格存储的值无关，而是与行和列的组合存储在其中.

In my data frame, I want to replace certain blank cells and cells with values with NA. But the cells I want to replace with NAs has nothing to do with the value that cell stores, but with the combination of row and column it is stored in.

这是一个示例数据帧DF:

Here's a sample data frame DF:

  Fruits   Price   Weight   Number of pieces

  Apples      20      2          10
  Oranges     15      4          16
  Pineapple   40      8           6
  Avocado     60      5          20

我想将Pineapple'e的重量替换为NA，将Orange的件数替换为NA.

I want to replace Pineapple'e weight to NA and Orange's number of pieces to NA.

DF$Weight[3] <- NA
DF$`Number of pieces`[2] <- NA  

这将替换存储在该位置中并且可能会更改的任何值.我想使用特定的行和列名称进行此替换，因此值的位置变得无关紧要.

This replaces any value that's stored in that position and that may change. I want to use specific row and column names to do this replacement so the position of value becomes irrelevant.

输出:

 Fruits   Price   Weight   Number of pieces

  Apples      20      2          10
  Oranges     15      4          NA
  Pineapple   40      NA           6
  Avocado     60      5          20

但是，如果更改表的顺序，这将用NA替换错误的值.

But if order of the table is changed, this would replace wrong values with NA.

我应该怎么做?