I have a pretty messy vector like this:

```
purchase <- c('group1apple:45pear:50peach32apple15','group2peach25banana34apple15orange35','group3grape300peach42apple54pear35')

```

and I want extract the number after all `apple:`, which means I wang to get a output like:

`apple <- c(45,15,15,54)`

I tried`str_extract(purchase, "(?i)(?<=apple:\\D)\\d+")`
but not work.