<p>I know nothing about GAMs, but to me this Q looks clearly on-topic; I am surprised to see that there is so much controversy about it. The question did not simply ask about the meaning of <code>te()</code> and <code>ti()</code>; OP wrote that they are aware of the difference but expect them to coincide in this particular case for this particular reason; however they observe slight discrepancy. To me, this practically screams "on-topic": the models must be different but presumably in a tricky way, and it must require quite a bit of statistical knowledge to tell them apart. This is not at all a programming question.</p>

<p>Moreover, this must have become even more clear after @Gavin posted his insightful answer which is, frankly, quite obviously statistical and not programming-ish.</p>

<p>We have lots of open, popular, well-upvoted and highly insightful threads starting with questions about why some two functions in some statistical environment(s) produce different results. Like e.g. why an <code>anova</code> call produces different p-values from an <code>lm</code> call in R, or why <code>lme4</code> in R does something different from <code>PROC MIXED</code> in SAS, or why <code>eig</code> and <code>svd</code> yield different signs in Matlab, or whatnot. I strongly believe that all of that should be on topic here.</p>

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<p><strike>Gavin's answer was posted on the 13th. It was accepted on the 13th too, indicating that this indeed resolved OP's issue. The post then got closed on the 14th meaning that some of the people voting to close must have already been able to see Gavin's answer. But okay -- after the closure on the 14th, Gavin posted a comment explaining why this should be on-topic and started the reopen voting. And <em>then</em>, after four reopen votes the thread was kicked out of the queue by Peter's leave-closed vote.</strike> Update: @gung made some fair comments about how the review queue works and I am now "striking" part of my original answer that was about specifics of how this particular Q got closed. This is not the most important here anyway.</p>
