编码加权平均值（R）

Question

I am having trouble with a piece of my code. I want to perform a weighted mean but the value I get is not the value I obtain if I calculate the weighed mean myself.

Here's how I'm coding the weighted mean:

weighted.mean(x = dataset$A[rows], weights = weights) 

The variable is "dataset$A" and the rows I'm using for the weighted mean are listed in "rows" (there are 2 rows). The weights are listed in "weights."

Here's how I'm calculating it myself:

dataset$A_MEAN[rows[1]]*weights[1] + dataset$A_MEAN[rows[2]]*weights[2]

Why is there a difference with these two lines of code? I tried with the following values:

dataset$A = [45792.76, 64984.67] 
weights = [0.3253927, 0.6746073]

The first line of code returns: 55388.71 The second line of code returns: 58739.76

Thank you so much! I am sure that this is something minor, but it's driving me nuts!

Answer 1

Check your use of weighted.mean

The arguments weights should be w :

weighted.mean(x = dataset$A[rows], w = weights) should give you what you want.

When calling a function, you can make sure that you're using the correct variable names by reading the function's documentation with ?weighted.mean