Re: [R] Plot with x-axis dates

2009-02-07 Thread Gabor Grothendieck
On Sat, Feb 7, 2009 at 6:10 AM, Duncan Murdoch  wrote:
> On 06/02/2009 4:48 PM, Paul Warren Simonin wrote:
>>
>> Hello,
>>   I am attempting to create plots using two continuous variables and  it
>> seems I should be able to use the simple "plot" command. However,  my x-axis
>> values are dates, and I believe this could be the reason I  am receiving
>> error messages reading:
>>
>> Error in Summary.factor(c(2L, 4L, 3L, 5L, 6L, 7L, 1L), na.rm = FALSE) :
>>   range not meaningful for factors
>>
>> I have attempted to convert the date values to official dates within R
>>  and have done that successfully using the as.date function, but this  did
>> not help in the plots. So, how can one create plots in which the  x-axis is
>> date values? I know it would be possible to convert all my  dates into a
>> different linear scale (e.g., julian dates). However, I  would like to
>> complete this process as simply as possible.
>
> You can do plots using dates on the axis, e.g.
>
> dates <- ISOdate(2009, 1:12, 1) # first of every month
> plot(dates, 1:12)

I would be a bit careful here since there could be some
misalignment due to GMT vs. current time zone depending
on what you have.   See R News 4/1 for more.

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Re: [R] Plot with x-axis dates

2009-02-07 Thread Duncan Murdoch

On 06/02/2009 4:48 PM, Paul Warren Simonin wrote:

Hello,
   I am attempting to create plots using two continuous variables and  
it seems I should be able to use the simple "plot" command. However,  
my x-axis values are dates, and I believe this could be the reason I  
am receiving error messages reading:


Error in Summary.factor(c(2L, 4L, 3L, 5L, 6L, 7L, 1L), na.rm = FALSE) :
   range not meaningful for factors

I have attempted to convert the date values to official dates within R  
and have done that successfully using the as.date function, but this  
did not help in the plots. So, how can one create plots in which the  
x-axis is date values? I know it would be possible to convert all my  
dates into a different linear scale (e.g., julian dates). However, I  
would like to complete this process as simply as possible.


You can do plots using dates on the axis, e.g.

dates <- ISOdate(2009, 1:12, 1) # first of every month
plot(dates, 1:12)

Now sometimes the default tick choices for dates don't look great, e.g.

plot(dates[1:3], 1:3)

only gets two ticks labelled Jan and Mar, but you can specify your own 
locations and labels:


plot(dates[1:3], 1:3, xaxt="n")
axis(1, at=dates[1:3], labels=format(dates[1:3], "%b %d"))

Duncan Murdoch

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