How to predict/interpolate new Y given knwon Xs and Ys?
I see, so predict is mono-directional: only gives x with a know y but not the other way round. Thank you On Tue, Jan 26, 2021 at 10:20 AM Jeff Newmiller
<jdnewmil at dcn.davis.ca.us> wrote:
model2 <- lm( x~y ) predict(model2, data.frame(y=26)) model2 is however not the inverse of model... if you need that then you need to handle that some other way than using predict, such as an invertible monotonic spline (or in this case a little algebra). On January 26, 2021 1:11:39 AM PST, Luigi Marongiu <marongiu.luigi at gmail.com> wrote:
Hello, I have a series of x/y and a model. I can interpolate a new value of x using this model, but I get funny results if I give the y and look for the correspondent x: ```
x = 1:10 y = 2*x+15 model <- lm(y~x) predict(model, data.frame(x=7.5))
1 30
predict(model, data.frame(y=26))
1 2 3 4 5 6 7 8 9 10 17 19 21 23 25 27 29 31 33 35 Warning message: 'newdata' had 1 row but variables found have 10 rows
data.frame(x=7.5)
x 1 7.5
data.frame(y=26)
y 1 26 ``` what is the correct syntax? Thank you Luigi
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-- Sent from my phone. Please excuse my brevity.
Best regards, Luigi