Dear Mr. Song, S orry for the late response.
My response to you, is that, first, y ou are not assuming a linear relationship in your formula, because the argument k of your smooth term s() is not 1. Now, I cannot see figure 1, but you can obtain figure 2 from the formula that you describe here. In order to obtain a plot with the derivative, you have to create a ne w column in your matrix or data-frame that is the derivative of the blood pressure, and then apply gam() as in ct=gam( derivative( Blood pressure ) ~s(Temp,k=5)+s(BMI,k=4)+s(Age,k=6)+s(RH,k=4)+s(Pa,k= 5)+Gender+Season,family=gaussian,data=mydata) . H ope that helps . Best regards, Jue On Saturday, 12 November 2016, <r-help-requ...@r-project.org> wrote: > > > Date: Fri, 11 Nov 2016 17:31:23 +0800 (GMT+08:00) > From: ??? <songx...@lzu.edu.cn> > To: r-help@r-project.org > Subject: [R] > > Message from Lanzhou University, China. (Help) > Message-ID: <6f90a404.73da.15852ba30a2.coremail.songx...@lzu.edu.cn> > Content-Type: text/plain; charset="utf-8" > > Dear moderators, > I am a student come from Lanzhou University, Gansu, China. I have two > questions on R (mgcv), which puzzled me for a long time. I did not find > answer in Chinese forum. I hope you could answer me in your free time or > post it in R-help. Thank you very much. > > Xuping Song > > 2016.11.11 > We want to investigate the association between exposure to ambient > temperature and blood pressure. The ?mgcv? package was used to perform GAM > analyses in R. This is the formula. > > ct=gam(Blood pressure~s(Temp,k=5)+s(BMI,k=4)+s(Age,k=6)+s(RH,k=4)+s(Pa,k= > 5)+Gender+Season,family=gaussian,data=mydata) > > I have two questions. Firstly, personal characteristic (Age, Gender, BMI > and Season) could influence blood pressure. How to control these variables? > BMI and Age are continuous variable. I smoothed these two variables like > formula 1. Season (1,2,3,4) and Gender(0,1) were add to formula, which were > assumed as linear relationship. Is that right? > > Secondly, I want to get plot 2, which x-axis presented ?Temperature? and > y-axis presented ?Change in Blood Pressure for every 1?C decrease of > temperature?. Plot 2 came from a paper published recently (see appendix). > Therefore, I ran formula 1 in R and run ?plot(ct)?. Then I get plot 1. I > don?t understand the meaning of ?s?Tmean?3.87?? in y-axis. Does it > represent ?Blood pressure?? If the hypothesis is right, plot 2 is the > derivative of plot 1. However, I don?t know the specific code. I am a > beginner of R and this problem puzzled me for a long time. Please help me. > Thank you very much. > -------------- next part -------------- > A non-text attachment was scrubbed... > Name: Paper (plot 2).pdf > Type: application/pdf > Size: 913655 bytes > Desc: not available > URL: <https://stat.ethz.ch/pipermail/r-help/attachments/20161111/ > 4c9d7aec/attachment.pdf> > -------------- next part -------------- > A non-text attachment was scrubbed... > Name: Plot 2.png > Type: image/png > Size: 37455 bytes > Desc: not available > URL: <https://stat.ethz.ch/pipermail/r-help/attachments/20161111/ > 4c9d7aec/attachment.png> > > [[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.