HiI have a set of data with two independent variables, a pretest (covariate) and posttest (dependent variable).Can anyone help me run robust ANCOVA?If you wish I can send you the data file.yours [[alternative HTML version deleted]]
Hi Hamid, This looks a bit like a repeated measures analysis, but for a simple introduction to ANCOVA using R see the latter part of the following: http://www.stat.columbia.edu/~martin/W2024/R8.pdf Jim On Mon, Mar 28, 2016 at 3:52 AM, HAMID REZA ASHRAFI via R-help <r-help at r-project.org> wrote:> HiI have a set of data with two independent variables, a pretest (covariate) and posttest (dependent variable).Can anyone help me run robust ANCOVA?If you wish I can send you the data file.yours > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at 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.
> On Mar 27, 2016, at 9:52 AM, HAMID REZA ASHRAFI via R-help <r-help at r-project.org> wrote: > > HiI have a set of data with two independent variables, a pretest (covariate) and posttest (dependent variable).Can anyone help me run robust ANCOVA?If you wish I can send you the data file.yours > [[alternative HTML version deleted]]https://cran.r-project.org/web/views/Robust.html help(pac=MASS, rlm) # A starting point perhaps: MASS::rlm( Post ~ pre +IV1 + IV2, data=yourdataframe) -- David Winsemius Alameda, CA, USA
>>>>> David Winsemius <dwinsemius at comcast.net> >>>>> on Sun, 27 Mar 2016 19:30:31 -0700 writes:>> On Mar 27, 2016, at 9:52 AM, HAMID REZA ASHRAFI via >> R-help <r-help at r-project.org> wrote: >> >> HiI have a set of data with two independent variables, a >> pretest (covariate) and posttest (dependent variable).Can >> anyone help me run robust ANCOVA?If you wish I can send >> you the data file.yours [[alternative HTML version >> deleted]] > https://cran.r-project.org/web/views/Robust.html > help(pac=MASS, rlm) > # A starting point perhaps: > MASS::rlm( Post ~ pre +IV1 + IV2, data=yourdataframe) > David Winsemius Alameda, CA, USA Indeed. Or use the more sophisticated (and somewhat more robust / efficient) methods from package 'robustbase' install.packages("robustbase") require("robustbase") fm <- lmrob(Post ~ pre +IV1 + IV2, setting = "KS2014", data=yourdataframe) where recent research lead to the recommendation of setting="KS2014", which indeed maybe relevant for "ANCOVA". Martin Maechler, ETH Zurich (and maintainer of 'robustbase', hence "biased" !)