[R] Using R to fit a curve to a dataset using a specific equation

[Michael Eisenring]

Hi there

 

	
I would like to use a specific equation to fit a curve to one of my data
sets (attached)

> dput(data)

structure(list(Gossypol = c(1036.331811, 4171.427741, 6039.995102,
5909.068158, 4140.242559, 4854.985845, 6982.035521, 6132.876396,
948.2418407, 3618.448997, 3130.376482, 5113.942098, 1180.171957,
1500.863038, 4576.787021, 5629.979049, 3378.151945, 3589.187889,
2508.417927, 1989.576826, 5972.926124, 2867.610671, 450.7205451, 1120.955,
3470.09352, 3575.043632, 2952.931863, 349.0864019, 1013.807628, 910.8879471,
3743.331903, 3350.203452, 592.3403778, 1517.045807, 1504.491931,
3736.144027, 2818.419785, 723.885643, 1782.864308, 1414.161257, 3723.629772,
3747.076592, 2005.919344, 4198.569251, 2228.522959, 3322.115942,
4274.324792, 720.9785449, 2874.651764, 2287.228752, 5654.858696,
1247.806111, 1247.806111, 2547.326207, 2608.716056, 1079.846532), Treatment
= structure(c(2L, 3L, 4L, 5L, 2L, 3L, 4L, 5L, 1L, 2L, 3L, 5L, 1L, 2L, 3L,
4L, 5L, 1L, 2L, 3L, 4L, 5L, 1L, 2L, 3L, 4L, 5L, 1L, 2L, 3L, 4L, 5L, 1L, 2L,
3L, 4L, 5L, 1L, 2L, 3L, 4L, 5L, 1L, 2L, 3L, 4L, 5L, 1L, 2L, 3L, 4L, 5L, 1L,
2L, 3L, 1L), .Label = c("C", "1c_2d", "3c_2d", "9c_2d", "1c_7d"), class =
"factor"), Damage_cm = c(0.4955, 1.516, 4.409, 3.2665, 0.491, 2.3035, 3.51,
1.8115, 0, 0.4435, 1.573, 1.8595, 0, 0.142, 2.171, 4.023, 4.9835, 0, 0.6925,
1.989, 5.683, 3.547, 0, 0.756, 2.129, 9.437, 3.211, 0, 0.578, 2.966, 4.7245,
1.8185, 0, 1.0475, 1.62, 5.568, 9.7455, 0, 0.8295, 2.411, 7.272, 4.516, 0,
0.4035, 2.974, 8.043, 4.809, 0, 0.6965, 1.313, 5.681, 3.474, 0, 0.5895,
2.559, 0)), .Names = c("Gossypol", "Treatment", "Damage_cm"), row.names =
c(NA, -56L), class = "data.frame")

The equation is: y~yo+a*(1-b^x) Where: y =Gossypol (from my data set) x=
Damage_cm (from my data set)

The other 3 parameters are unknown: yo=Intercept, a= assymptote ans b=slope 

In the end I would like to use the equation to plot a curve (with SE
interval, I usually use ggplot2)

Furthermore, I would like to know the R2 and p value. I would also be
interested in the parameters yo , a and b

I have never done this before and would be extremely grateful if anyone
could help me? I suppose I have to use a non linear approach (glm(...)). I
found out that the mosaic package might be helpful.

thanks a lot, Mike

 


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