[R] Why can't I access this type?

[Yves S. Garret]

Hi, I'm just learning my way around R.  I got a bunch of states and would
like to access to get all of the ones where it's cold.  But when I do the
following, I will get the following error:

> all.states <- as.data.frame(state.x77)
> cold.states <- all.states[all.states$Frost > 150, c("Name", "Frost")]
Error in `[.data.frame`(all.states, all.states$Frost > 150, c("Name",  :
  undefined columns selected

I don't get it.  When I look at all.states, this is what I see:

> str(all.states)
'data.frame':   50 obs. of  8 variables:
 $ Population: num  3615 365 2212 2110 21198 ...
 $ Income    : num  3624 6315 4530 3378 5114 ...
 $ Illiteracy: num  2.1 1.5 1.8 1.9 1.1 0.7 1.1 0.9 1.3 2 ...
 $ Life Exp  : num  69 69.3 70.5 70.7 71.7 ...
 $ Murder    : num  15.1 11.3 7.8 10.1 10.3 6.8 3.1 6.2 10.7 13.9 ...
 $ HS Grad   : num  41.3 66.7 58.1 39.9 62.6 63.9 56 54.6 52.6 40.6 ...
 $ Frost     : num  20 152 15 65 20 166 139 103 11 60 ...
 $ Area      : num  50708 566432 113417 51945 156361 ...

What am I messing up?

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