Hi I have been doing theR-exercises to improve my R programming capabilities.
Data.frame exercise4 showed me that I have a languageproblem. Yes, I am
frustrated, but please don’t take this as acriticism of the R language.
Theroutines I have managed to write do marvelous things in a short period
oftime. I really want to do more, but thisis a steep rocky thick with
underbrush hill that is not fun to climb. But there are good resources. Swirl
is wonderful. My thanks to the authors of thatpackage. Jared Lander’s R for
Everyoneis a really good beginners book. DataCamp, Coursera, all informative
courses. Yes I’m frustrated. After a couple of years on and off
takingclasses, reading books, reading stack overflow and r-help just about
daily, Iam learning to almost crawl. At one timeI thought I had advanced to
walking but days like today show me I’m a toddlerabout to fall on his backside.
Reading the manuals onCRAN is analogous to reading the tax code. Without a
specific objective for motivation, reading them is either painfulor a certain
cure for insomnia. Here's the problem Ireferred to at the beginning and my
"solution". # Exercise 4 fromR Exercises# Create a simpledata frame from 3
vectors. Order the entire data frame by the# first column.df2 <- data.frame(a
=5:1,b = letters[1:5], c = runif(5))order(df2$a) Naturally the orderfunction
did nothing. But I did read the help page and thought I followedit. And
there is no obvious environmentissue. It’s a simple data.frame and Iwant to
order it by one column. Such asdf2 <- data.table(df2)setkey(df2, a). Done. No
fuss, no muss, no needing “with”. Per "help"Description order returns
apermutation which rearranges its first argument into ascending or
descendingorder, breaking ties by further arguments. sort.list is the same,
using onlyone argument.See the examples for howto use these functions to sort
data frames, etc. Usage order(..., na.last =TRUE, decreasing = FALSE,
method = c("shell", "radix")) sort.list(x, partial =NULL, na.last = TRUE,
decreasing = FALSE, method = c("shell", "quick","radix"))Arguments ...
a sequence of numeric,complex, character or logical vectors, all of the same
length, or a classed Robject. Well, doesn't ... meanany legal object? I gave
it a legal object and got nada. And the answerabsolutely has me screaming "Say
What"df2[with(df2,order(a)),] What's with "with? In Mr. Lander’s book, page
126, “Here we used a new function, with. This allows us to specify the columns
of adata frame without having to specify the data.frame name each time.”
Great, I’m a horrible typist and will takeany and all typing shortcuts.
However, Idon’t use it because I don’t understand what it does. Obviously it’s
important, but I’m stuck on why or how I would use it. It is one function I
donot use because I find it incomprehensible. To witEvaluate an R expressionin
an environment constructed from data, possibly modifying (a copy of)
theoriginal data. First of all, if I'm notmodifying data (or as a subset
activity creating data), why am I doing whateverit is I'm doing? ("possibly
modifying (a copy of) the originaldata.") Possibly?? Evaluate. According to the
thesaurus a) assess(v), b) appraise, c) gage. OK, am I in a safe area? I'll
evaluate that. Do I desire future social contact with thisperson? I'll
evaluate that. In no way do I ever evaluatean equation. I may attempt to solve
it. I may do a computer programto do the calculations and return a result. I
will probably evaluate theresult as to whether or not it helps solve the
problem. Think in terms ofan income tax return. But evaluate an R expression?
No clue whatthat might mean. And that is my problemin a nutshell. The
remainder of thedefinition is also obtuse. an R expression in an
environmentconstructed from data. Why would one make an environment
withoutdata? Obviously I am missing thepoint. My own created function makes a
new environment, but I onlycreated it to crunch numbers. If it doesn't crunch
numbers it's useless. The point is, I do not understand the definitionof "with"
and thus have no idea how to use it. I guesscomputerese is analogous to
taxlawese. Familiar words have entirely different meanings. Carl Sutton CPA
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