Yes, this was written a bit bone-headed (as I am allowed to say...) If you look at the code, you will see inside:
a <- anova(lm(freq ~ score, data = list(freq = x/n, score = as.vector(score)), weights = w)) and the lm() inside should give you the direction via the sign of the regression coefficient on "score". So, at least for now, you could just doctor a copy of the code for your own purposes, as in fit <- lm(freq ~ score, data = list(freq = x/n, score = as.vector(score)), weights = w) a <- anova(fit) and arrange to return coef(fit)["score"] at the end. Something like structure(... estimate=c(lpm.slope=coef(fit)["score"]) ....) (I expect that you might also extract the t-statistic from coef(summary(fit)) and find that it is the signed square root of the Chi-square, but I won't have time to test that just now.) -pd > On 8 Sep 2023, at 07:22 , Thomas Subia via R-help <r-help@r-project.org> > wrote: > > Colleagues, > > Thanks all for the responses. > > I am monitoring the daily total number of defects per sample unit. > I need to know whether this daily defect proportion is trending upward (a bad > thing for a manufacturing process). > > My first thought was to use either a u or a u' control chart for this. > As far as I know, u or u' charts are poor to detect drifts. > > This is why I chose to use prop.trend.test to detect trends in proportions. > > While prop.trend.test can confirm the existence of a trend, as far as I know, > it is left to the user > to determine what direction that trend is. > > One way to illustrate trending is of course to plot the data and use > geom_smooth and method lm > For the non-statisticians in my group, I've found that using this method > along with the p-value of prop.trend.test, makes it easier for the users to > determine the existence of trending and its direction. > > If there are any other ways to do this, please let me know. > > Thomas Subia > > > > > > > > > > > > > On Thursday, September 7, 2023 at 10:31:27 AM PDT, Rui Barradas > <ruipbarra...@sapo.pt> wrote: > > > > > > Às 14:23 de 07/09/2023, Thomas Subia via R-help escreveu: >> >> Colleagues >> >> Consider >> smokers <- c( 83, 90, 129, 70 ) >> patients <- c( 86, 93, 136, 82 ) >> >> prop.trend.test(smokers, patients) >> >> Output: >> >> Chi-squared Test for Trend inProportions >> >> data: smokers out of patients , >> >> using scores: 1 2 3 4 >> >> X-squared = 8.2249, df = 1, p-value = 0.004132 >> >> # trend test for proportions indicates proportions aretrending. >> >> How does one identify the direction of trending? >> # prop.test indicates that the proportions are unequal but doeslittle to >> indicate trend direction. >> All the best, >> Thomas Subia >> >> >> [[alternative HTML version deleted]] >> >> ______________________________________________ >> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >> 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. > Hello, > > By visual inspection it seems that there is a decreasing trend. > Note that the sample estimates of prop.test and smokers/patients are equal. > > > smokers <- c( 83, 90, 129, 70 ) > patients <- c( 86, 93, 136, 82 ) > > prop.test(smokers, patients)$estimate > #> prop 1 prop 2 prop 3 prop 4 > #> 0.9651163 0.9677419 0.9485294 0.8536585 > > smokers/patients > > #> [1] 0.9651163 0.9677419 0.9485294 0.8536585 > > plot(smokers/patients, type = "b") > > > > Hope this helps, > > Rui Barradas > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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. -- Peter Dalgaard, Professor, Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Office: A 4.23 Email: pd....@cbs.dk Priv: pda...@gmail.com ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.