Hello R-help 
I have the following data for a standard curve
concentration(nM),fluorescence
0,48.34
2,58.69
5,70.83
10,94.73
20,190.8
50,436.0
100, 957.9
 
(1)Is there function in R to plot a spline.
(2)How can I interpolation,say 1000 point from 0nM-100nM and store this as a 
data frame of concentration,fluorescence
(3)How can I modify the code below so that instead of retrieving a concentration 
with the exact value of fluorescence, it gives me concentration for the value 
that is closest to that fluorescence.
 
subset(df,fluorescence==200.3456,select=concentration)


      
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