new example for vignette

[momeara]

Hi what a nice package--

Perhaps you'd like to add to your vignette that it's easy to check that a data frame column contains a column

data.frame(a=c(1,2,3)) %>%
    verify("a" %>% exists) %>%    # ok
    verify("b" %>% exists)        # fails

[tonyfischetti]

Thanks for the kind words! That would be super useful. Because of the nested magrittr pipes, do you have any idea what exists would look like?

[momeara]

Exists already exists! If you try it, you'll see it works with the current version of assertr : D

[tonyfischetti]

Just checked this. It will return TRUE is there's a variable named the same name as the column to be checked...

mpgg <- "this"
mtcars %>%
  verify("mpgg" %>% exists) %>%
  head # passes

Which can be really dangerous.
So you have to do this instead

mpgg <- "this"
mtcars %>%
  verify(exists("mpgg", where=.)) %>%
  head # fails

I think it might be worth writing a dedicated wrapper function (I'll do it!).
What do you think?

[momeara]

Nice catch, yes, in this case a wrapper would be helpful.

On Sat, Aug 15, 2015 at 11:48 AM, Tony Fischetti notifications@github.com
wrote:

Just checked this. It will return TRUE is there's a variable named the
same name as the column to be checked...

mpgg <- "this"mtcars %>%
verify("mpgg" %>% exists) %>%
head # passes

Which can be really dangerous.
So you have to do this instead

mpgg <- "this"mtcars %>%
verify(exists("mpgg", where=.)) %>%
head # fails

I think it might be worth writing a dedicated wrapper function (I'll do
it!).
What do you think?

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#23 (comment)
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[tonyfischetti]

Because I don't have any other "predicates" that can't be used with verify and not the other verbs I don't think I'm gonna write the wrapper function, but I'm gonna put it in the vignette!

[tonyfischetti]

I decided to implement this after all! It's has_all_names :) Thanks for the suggestion!

It's in the README and vignette now, too

[momeara]

👍