我正在尝试计算没有缺失值的加权百分比。关于如何修改下面的代码，使NA值不属于分析的一部分，有什么建议吗？

df <- data.frame(
    wave = rep(c(1,2),6),
    gender = rep(c("m", "f", NA),4),
    exp = rep(c("c", "e", NA),4),
    weights = rnorm(12, 1, .5)
)

> head(df)
  wave gender  exp   weights
1    1      m    c 0.6556222
2    2      f    e 0.6462524
3    1   <NA> <NA> 1.1822910
4    2      m    c 1.3842665
5    1      f    e 0.9438269
6    2   <NA> <NA> 1.4405539

 library(srvyr)
 library(tidyverse)

df %>% 
  gather(key, value, gender, exp) %>%
  as_survey_design(1, weight = weights) %>%
  dplyr::group_by(wave, key, value)  %>%
  dplyr::summarise(prop_weighted=srvyr::survey_mean(na.rm=TRUE)*100) 

# A tibble: 12 × 5
# Groups:   wave, key [4]
    wave key    value prop_weighted prop_weighted_se
   <dbl> <chr>  <chr>         <dbl>            <dbl>
 1     1 exp    c              27.0             18.1
 2     1 exp    e              38.7             21.7
 3     1 exp    NA             34.3             20.3
 4     1 gender f              38.7             21.7
 5     1 gender m              27.0             18.1
 6     1 gender NA             34.3             20.3
 7     2 exp    c              27.6             19.8
 8     2 exp    e              20.3             14.8
 9     2 exp    NA             52.1             23.0
10     2 gender f              20.3             14.8
11     2 gender m              27.6             19.8
12     2 gender NA             52.1             23.0