Re: [R] physical constraint with gam

2016-05-16 Thread Dominik Schneider
Thanks for the clarification! On Sat, May 14, 2016 at 1:24 AM, Simon Wood wrote: > On 12/05/16 02:29, Dominik Schneider wrote: > > Hi again, > I'm looking for some clarification on 2 things. > 1. On that last note, I realize that s(x1,x2) would be the other obvious > interaction to compare with

Re: [R] physical constraint with gam

2016-05-14 Thread Simon Wood
On 12/05/16 02:29, Dominik Schneider wrote: > Hi again, > I'm looking for some clarification on 2 things. > 1. On that last note, I realize that s(x1,x2) would be the other > obvious interaction to compare with - and I see that you recommend > te(x1,x2) if they are not on the same scale. - yes th

Re: [R] physical constraint with gam

2016-05-13 Thread Simon Wood
On 11/05/16 17:11, Dominik Schneider wrote: > Hi Simon, Thanks for this explanation. > To make sure I understand, another way of explaining the y axis in my > original example is that it is the contribution to snowdepth relative > to the other variables (the example only had fsca, but my actual c

Re: [R] physical constraint with gam

2016-05-11 Thread Dominik Schneider
Hi again, I'm looking for some clarification on 2 things. 1. On that last note, I realize that s(x1,x2) would be the other obvious interaction to compare with - and I see that you recommend te(x1,x2) if they are not on the same scale. 2. If s(x1,by=x1) gives you a "parameter" value similar to a GLM

Re: [R] physical constraint with gam

2016-05-11 Thread Dominik Schneider
Hi Simon, Thanks for this explanation. To make sure I understand, another way of explaining the y axis in my original example is that it is the contribution to snowdepth relative to the other variables (the example only had fsca, but my actual case has a couple others). i.e. a negative s(fsca) of -

Re: [R] physical constraint with gam

2016-05-11 Thread Simon Wood
The spline having a positive value is not the same as a glm coefficient having a positive value. When you plot a smooth, say s(x), that is equivalent to plotting the line 'beta * x' in a GLM. It is not equivalent to plotting 'beta'. The smooths in a gam are (usually) subject to `sum-to-zero' id

Re: [R] physical constraint with gam

2016-05-11 Thread David Winsemius
> On May 10, 2016, at 5:30 PM, Dominik Schneider > wrote: > > Hi, > Just getting into using GAM using the mgcv package. I've generated some > models and extracted the splines for each of the variables and started > visualizing them. I'm noticing that one of my variables is physically > unrealis