[R] How to use strings from a data.frame as the argument of an expression() for plot

2006-12-20 Thread MrJ Man 
Greetings,

I would like to use a data.frame with strings to feed
the expression() in the title of a plot. The way I did
this is:

molecules
-data.frame(name=c(o3,no,no2),expression=c(quote(O[3]),quote(NO),quote(NO[2])))

for (mol in c(5,7,9)) {
 plot(x, y, type=b,
main=eval(substitute(expression(paste(mol, Year
2005)),
 
list(mol=eval(parse(,text=toString(molecules$expression[(mol-3)/2])))
}

However, this looks cumbersome and I'm sure there is a
way to do this in R that is much more simple. The
complexity of the expression above is mainly due to
the fact that the only way I could find to convert a
string read from a data.frame into a symbol was to
enclose it in quote(symbol) and call toString on the
result, since selecting string data from a data.frame
returns an object that is not a string (why is this
so? A data.frame with doubles returns doubles).

What do you think?

Thanks in advance.

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Re: [R] How to use strings from a data.frame as the argument of an expression() for plot

2006-12-20 Thread Gabor Grothendieck 
Try this:


e - expression(O[3], NO, NO[2])
opar - par(mfrow = c(2,2))
for(i in 1:3) plot(1, 1, type = b, main = bquote(.(e[[i]]) ~ Year ~ 2005))
par(opar)

Also please read the last line to every post to r-help and particularly note
the part about reproducible examples.   x and y.were undefined.

On 12/20/06, MrJ Man [EMAIL PROTECTED] wrote:
 Greetings,

 I would like to use a data.frame with strings to feed
 the expression() in the title of a plot. The way I did
 this is:

 molecules
 -data.frame(name=c(o3,no,no2),expression=c(quote(O[3]),quote(NO),quote(NO[2])))

 for (mol in c(5,7,9)) {
  plot(x, y, type=b,
 main=eval(substitute(expression(paste(mol, Year
 2005)),

 list(mol=eval(parse(,text=toString(molecules$expression[(mol-3)/2])))
 }

 However, this looks cumbersome and I'm sure there is a
 way to do this in R that is much more simple. The
 complexity of the expression above is mainly due to
 the fact that the only way I could find to convert a
 string read from a data.frame into a symbol was to
 enclose it in quote(symbol) and call toString on the
 result, since selecting string data from a data.frame
 returns an object that is not a string (why is this
 so? A data.frame with doubles returns doubles).

 What do you think?

 Thanks in advance.

 __
 R-help@stat.math.ethz.ch mailing list
 https://stat.ethz.ch/mailman/listinfo/r-help
 PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
 and provide commented, minimal, self-contained, reproducible code.


__
R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

Re: [R] How to use strings from a data.frame as the argument of an expression() for plot

2006-12-20 Thread MrJ Man 
Thanks for your response; one more thing: Is it
possible to use a data.frame 
for the same effect, as these values are associated
with some others (I could 
of course use them separately, but merging them in a
data.frame should be 
possible in R)?

 Try this:


 e - expression(O[3], NO, NO[2])
 opar - par(mfrow = c(2,2))
 for(i in 1:3) plot(1, 1, type = b, main =
bquote(.(e[[i]]) ~ Year ~
 2005)) par(opar)

 Also please read the last line to every post to
r-help and particularly
 note the part about reproducible examples.   x and
y.were undefined.


__
R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

Re: [R] How to use strings from a data.frame as the argument of an expression() for plot

2006-12-20 Thread Gabor Grothendieck 
Just store them as strings in the data frame and then perform a conversion
to expressions prior to the loop:


DF - data.frame(s = c(O[3], NO, NO[2]), stringsAsFactors = FALSE)
e - parse(text = DF$s)
... continue with prior solution ...

On 12/20/06, MrJ Man [EMAIL PROTECTED] wrote:
 Thanks for your response; one more thing: Is it
 possible to use a data.frame
 for the same effect, as these values are associated
 with some others (I could
 of course use them separately, but merging them in a
 data.frame should be
 possible in R)?

  Try this:
 
 
  e - expression(O[3], NO, NO[2])
  opar - par(mfrow = c(2,2))
  for(i in 1:3) plot(1, 1, type = b, main =
 bquote(.(e[[i]]) ~ Year ~
  2005)) par(opar)
 
  Also please read the last line to every post to
 r-help and particularly
  note the part about reproducible examples.   x and
 y.were undefined.
 


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__
R-help@stat.math.ethz.ch mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.