legend/plotmath/substitute problem
On 12/14/2006 5:05 PM, Philipp Pagel wrote:
Dear R Experts,
I am trying to produce a legend for a series of plots which are
generated in a loop. The legend is supposed to look like this:
2000: gamma=1.8
where gamma is replaced by the greek letter and both the year and the
value of gamma are stored in variables.
Everything works fine as long as I have only one data series:
year = 2001
g = 1.9
plot(1)
legend('top', legend=substitute(paste(year, ': ', gamma, '=', g), list(year=year, g=g)) )
My problem starts, when I want to put more than one series of data in
the plot and accordingly need one legend row per data series:
year1 = 2001
year2 = 2005
g1 = 1.9
g2 = 1.7
plot(1)
legend('top',
legend=c(
substitute(paste(year, ': ', gamma, '=', g), list(year=year1, g=g1)),
substitute(paste(year, ': ', gamma, '=', g), list(year=year2, g=g2))
)
)
This obviously does not produce the desired result. Apparently, I am not
generating a list of expressions, as intended. So I thought, maybe R uses a
variety of the recycling rule here and tried:
The problem is that legend wants an expression, but substitute() isn't
returning one, it's returning a call, and c(call1,call2) produces a list
of two calls, not an expression holding two calls. So the following
would work, but there might be something more elegant:
year1 = 2001
year2 = 2005
g1 = 1.9
g2 = 1.7
plot(1)
legend('top',
legend=c(
as.expression(substitute(paste(year, ': ', gamma, '=', g),
list(year=year1, g=g1))),
as.expression(substitute(paste(year, ': ', gamma, '=', g),
list(year=year2, g=g2)))
)
)
Duncan Murdoch
year = c(2001, 2005)
g = c(1.9, 1.7)
plot(1)
legend('top',
legend=list(
substitute(paste(year, ': ', gamma, '=', g), list(year=year, g=g)),
)
)
No succes, either...
I have read and re-read the documentation for legend, expression, substitute
and plotmath but can't figure it out. Even drinking a cup of tea prepared from
fine-cut man page printouts didn't lead to satori.
I'm probably missing something simple. Any hints are highly appreciated.
Thanks
Philipp