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From |
"Nick Cox" <n.j.cox@durham.ac.uk> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
RE: st: RE: Graph Bar: help! |

Date |
Wed, 28 Sep 2005 10:21:08 +0100 |

First, to repeat a point made gently by both Scott Merryman and myself, and explained prominently in the Statalist FAQ, please do _not_ use anything other than plain text to send posts to the list. No HTML, etc. My original reply to your question was longer and more detailed, but Scott's was more direct and nearer what you want. (1) Cf. Scott's solution, tweaked to show percents. Try . graph bar acexist, over(year) yla(0 .2 "20" .4 "40" .6 "60" .8 "80") ytitle(percent with audit committee) This works because it is short-hand for . graph bar (mean) acexist, over(year) yla(0 .2 "20" .4 "40" .6 "60" .8 "80") ytitle(percent with audit committee) (2) Cf. my solution I made up a dataset with exactly the frequencies given in your post. I guess the reason my code produces the wrong results for you is that you have missing values you didn't tell us about and which my code assumed not to exist. More careful code is egen pc = sum(acexist), by (year) egen total = sum(acexist < .), by(year) replace pc = 100 * pc / total but a more direct approach would be egen PC = mean(100 * acexist), by(year) and that doesn't need any tweaking to ensure the right answer if missings are present. After that it is graph bar PC, over(year) ... Nick n.j.cox@durham.ac.uk Katarina Sikavica dear nick cox and others: I have just tried to do as suggested in your e-mail below; that is, since I am using stata 8 I typed: egen pc = sum(acexist), by (year) egen total = sum(1), by(year) replace pc = 100 * pc / total I have also tried: bysort year: gen pc = sum(acexist) bysort year: replace pc = 100 * pc[_N] / _N .... but unfortunately I get twice the same wrong results: tabdisp year, cell(pc) shows: year pc 2000 12,09302 2001 28,50467 2002 62.61682 2003 71.02804 2004 74.4186 am I doing something wrong??? help!! Nick Cox Katarina's data are like this: . tab year acexist | acexist year | 0 1 | Total -----------+----------------------+---------- 2000 | 29 26 | 55 2001 | 24 61 | 85 2002 | 69 134 | 203 2003 | 56 152 | 208 2004 | 50 160 | 210 -----------+----------------------+---------- Total | 228 533 | 761 -graph bar- won't deliver the reduction she wants, at least not without some preparation. The reason is a little technical. -graph bar- is based mainly on a temporary reduction of the data using -collapse-, and -collapse- doesn't offer that reduction. (It is nearer the territory of -contract-, but that is a different story.) There are various solutions to the problem. A first solution is to generate your own percent variable and then plot that directly. Each percent is, we recall, a numerator divided by a total, multiplied by 100. One easy way to get the total is using -egen, total()-. In Stata 8 and earlier, the function here was -egen, sum()-, not -egen, total()-. . egen pc = total(acexist), by(year) . egen total = total(1), by(year) (what's 1 + 1 + 1 + ... + 1? the total number of observations) . replace pc = 100 * pc / total Stata diehards would scoff at this as namby-pamby and do it with -by:-. . bysort year: gen pc = sum(acexist) . by year: replace pc = 100 * pc[_N] / _N Either way, we can check that we are on the right lines by . tabdisp year, cell(pc) ---------------------- year | pc ----------+----------- 2000 | 47.27273 2001 | 71.76471 2002 | 66.00985 2003 | 73.07692 2004 | 76.19048 ---------------------- Then the graph is a line away: . graph bar (mean) pc, over(year) ytitle(percent with audit committee) yla(, ang(h)) Or . twoway bar pc year, ytitle(percent with audit committee) yla(, ang(h)) barw(0.5) Another solution employs a user-written program -catplot- from SSC. You can install that by . ssc install catplot -catplot- is just a wrapper for -graph bar- (or -graph hbar- or -graph dot-). It merely grinds through some reductions not quite trivial otherwise and then fires up a -graph- command. You can get a graph in one line with -catplot- without any prior calculation, although in practice I get there through a sequence of small experiments: . catplot bar acexist year, percent(year) stack asyvars yla(, ang(h)) yti(percent without and with audit committee) legend(order(1 "without" 2 "with")) A graph I like more follows a reversal of coding: . gen acexist2 = 1 - acexist . catplot bar acexist2 year, percent(year) stack asyvars yla(, ang(h)) yti(percent with audit committee) legend(off) bar(2, bcolor(none)) The original announcement of -catplot- contains some related comment. http://www.stata.com/statalist/archive/2003-02/msg00608.html Nick n.j.cox@durham.ac.uk Katarina Sikavica (edited, mainly to ASCII from HTML) I have just started with Stata graphics and have the following problem with -graph bar-: I have a dataset that contains data on the existence of audit committees -acexist-. In total there are 761 companies, 533 of them having an audit committee, 228 not. I would like to draw a -graph bar- that shows the increase in audit committee incidence over -year-. Drawing a -graph bar- on the increase in the number of audit committees works fine; however, as the data from 2000 and 2001 are of poor quality I would like to have percentages of audit committee incidence over the years 2000-2004 (that is: 47.27% (2000); 71.76% (2001); 66.01% (2002); 73.08% (2003); 76.19% (2004)). Neither of the following commands leads to the desired results: . graph bar (sum) acexist, over (year) percent . graph bar (sum) acexist, over (year) asyvar percentages * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

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