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# Re: st: number of dates in x axis

 From Maria Ana Vitorino To Subject Re: st: number of dates in x axis Date Tue, 24 May 2011 15:34:05 -0400

Hi Nick,
I really appreciate your help and patience.
Here is the code and some descriptives that may help to find the bug...
Thanks so much,
Ana

generate date1=date(date,"MY")

format date1 %tm
list date1 date in 1

+------------------+
|  date1      date |
|------------------|
1. | 3469m3   Aug2009 |
+------------------+

. egen newvar = axis(date1), label(date)

. tab newvar

date1 |      Freq.     Percent        Cum.
------------+-----------------------------------
Apr2009 |        119        4.38        4.38
Aug2009 |        130        4.78        9.15
Sep2009 |        126        4.63       13.79
Oct2009 |        126        4.63       18.42
Nov2009 |        134        4.93       23.35
Dec2009 |        151        5.55       28.90
Jan2010 |        153        5.62       34.52
Feb2010 |        150        5.51       40.04
Mar2010 |        150        5.51       45.55
Apr2010 |        149        5.48       51.03
May2010 |        146        5.37       56.40
Jul2010 |        153        5.62       62.02
Aug2010 |        151        5.55       67.57
Sep2010 |        153        5.62       73.20
Oct2010 |        153        5.62       78.82
Dec2010 |        161        5.92       84.74
Feb2011 |        142        5.22       89.96
Mar2011 |        154        5.66       95.62
Apr2011 |        119        4.38      100.00
------------+-----------------------------------
Total |      2,720      100.00

. sum date1

Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
date1 |      2720    18380.68    198.1158      17988      18718

. xtset person date1,  monthly
panel variable:  person (unbalanced)
time variable:  date1, 3459m1 to 3519m11, but with gaps
delta:  1 month

. forval i = 4(2)11 {
2.         local thisdate = mdy(`i', 1, 2009)
3.         local mydates `mydates' `thisdate'
4.         }

.
. display `thisdate'
18171

. display `mydates'
17988180491811018171

.
.
. local thisdate = mdy(4,1,2011)

. local mydates `mydates' `thisdate'

.
. display `thisdate'
18718

. display `mydates'
1798818049181101817118718

. xtline calories, overlay xlabel(`mydates', format(%d_m_Y) ang(v))
invalid label specifier, : 15341 15400 15461 15522 15584 15645 15645 17901 17960 18021 18082 18144 1820 > 5 17988 18049 18110 18171 18232 . . . . 18718 15341 15400 15461 15522 15584 15645 15706 15341 15400 15 > 461 15522 15584 15645 15706 17988 18049 18110 18171 18718 18718 18628 18628 18628 17898 17957 18018 18
> 079 18141 18628 18628:
r(198);

On May 24, 2011, at 3:05 PM, Nick Cox wrote:

You are burdening me with questions that I can't answer! You are not showing me the code that fails. Also, you are guessing again.

But it seems that you have daily dates.

Applying a %tm format to daily dates is legal but pointless. It gives you a result that does not apply to your dates.

The number 18110 is

(D) 1 August 2009 as a daily date

_but_

(M) March 3469 as a monthly date, i.e. a date almost 1460 years into the future. That's what

But that is not going to fail.

In my first post I gave an example of a format for daily dates that shows month and year: %d_m_Y.

I am going to try a third and last time. If you show me the code that fails, I will try to tell you your mistake. Otherwise what you don't tell us remains inscrutable.

Nick
n.j.cox@durham.ac.uk

Maria Ana Vitorino

Thanks. My code is a little more complicated than the example so I
didn't want to burden you with it. But I understand your position.
I think the issue has to do with the formatting of the date
variable...I can't seem to get it to work.
This is what I'm getting:

. generate date1=date(date,"MY")

. format date1 %tm

. list date1 date in 1

+------------------+
|  date1      date |
|------------------|
1. | 3469m3   Aug2009 |
+------------------+

What am I doing wrong?

Thanks,
Ana

On May 24, 2011, at 2:18 PM, Nick Cox wrote:

% sacrificial line.

Nick
n.j.cox@durham.ac.uk

-----Original Message-----
From: Nick Cox
Sent: 24 May 2011 19:16
To: 'statalist@hsphsun2.harvard.edu'
Subject: RE: st: number of dates in x axis

Please: I want to see the _exact_ code you typed. No commentary, no
paraphrase, no speculation. If you want to debug your code yourself,
feel free to do so. If you want me to try to debug your code, I am
might be wrong with your code.

Nick
n.j.cox@durham.ac.uk

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu
] On Behalf Of Maria Ana Vitorino
Sent: 24 May 2011 19:11
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: number of dates in x axis

I tried your code again (this time by pasting it into the do-file
editor instead into the command window) and it worked. But my version
is not working (I still get the invalid label specifier message).
Could it be because my time variable has gaps? Also, how can one setup
the "11" in your for loop without having to make mental calculations
regarding the number of months?
Thanks for the help!
Ana

On May 24, 2011, at 1:31 PM, Nick Cox wrote:

Yes. Show me the _exact_ code you typed.

Nick
n.j.cox@durham.ac.uk

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu
] On Behalf Of Maria Ana Vitorino
Sent: 24 May 2011 18:29
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: number of dates in x axis

Thanks Nick.
I tried running your example but I got the error message "invalid
label specifier, :  15341 15400 15461 ..."
Any suggestions?
Thanks!
Ana

On May 24, 2011, at 4:20 AM, Nick Cox wrote:

There is relevant material at

Stata 7: How can I get "nice" date labels on a graph?

http://www.stata.com/support/faqs/graphics/nicedate.html

"Note: This FAQ is relevant for users of releases prior to Stata 8.
For Stata 8 see update from 12 September 2003."

In fact the techniques there do remain useful for some problems.

Here's an example with different data. Here I decide that I want
labels every 2 months from 1 January 2002 to 1 January 2003. I loop
over the dates and put them in a bag, namely a local macro.

sysuse xtline1
xtset person day

forval i = 1(2)11 {
local thisdate = mdy(`i', 1, 2002)
local mydates `mydates' `thisdate'
}

local thisdate = mdy(1,1,2003)
local mydates `mydates' `thisdate'

xtline calories, overlay xlabel(`mydates', format(%d_m_Y) ang(v))

SJ-7-4  gr0030  . Stata tip 55: Better axis labeling for time
points/
intervals
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
N. J. Cox
Q4/07   SJ 7(4):590--592                                 (no
commands)
tip on labeling graphs for time points and time intervals

On Tue, May 24, 2011 at 4:45 AM, Maria Ana Vitorino
<vitorino@wharton.upenn.edu> wrote:

I have the following data:

+------------------------+
| Person   Weight      Date    |
|------------------------|
1. |  Name1       50      17988  |
2. |  Name1       55      18110  |
3. |  Name1       50      18141  |
4. |  Name1       45      18171  |
5. |    ...        .      . |
|------------------------|
6. |  Name2       85      18110 |
7. |  Name2       88      18171 |
8. |  Name3       68      17988 |
9. |    ...        .                       . |
10. |     ..        .      .                 |
|------------------------|
11. |  NameN        .               . |
+------------------------+

The labels for the date variables are the months' names (plus year)
(e.g.
"jan2006", "feb2007", etc)

If I do something like:

xtline Weight , overlay  i(Person) t(Date) xlab(, valuelabel)

The month names show up on the xaxis BUT only every 6 months or so.
How can
I control the number of "ticks" (AND month names ) that show up on
the
x-axis? (suppose I want a tick every 2 months or even every month)

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