[SOLVED] Parameterized RMarkdown does not filter parameter in R

Parameterized RMarkdown does not filter parameter in R

I am testing to use parameterized RMarkdown, using c as a parameter. I am using Knit with parameters choosing a or b, or nothing which by default chooses a. I expect to obtain 2 or 5 as the mean but I always obtain 3.5 which is the global mean. What am I doing wrong here?

---
title: "Parameterized RMarkdown"
output:
  html_document: default
params:
  c: "a"
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
library(tidyverse)
library(knitr)
```


```{r mean, echo=FALSE}
df <- tibble(c = c("a", "a", "a", "b", "b", "b"),
             x = c(1, 2, 3, 4, 5, 6))
mean(df$x)
```

Solution

We can add a filter on the extracted 'params' and get the mean of the column 'x'

library(dplyr)
df %>% 
    filter(c == params$c) %>%
    summarise(x = mean(x, na.rm = TRUE))

Or use base R to do this

with(df, mean(x[c == params$c], na.rm = TRUE))