How to calculate RNA copies in qPCR using R? I have these Ct data from qPCR for a series of samples A-H, I want to quantify the RNA copies of my samples using R:
Sample_ID   Replicate1_Ct Replicate2_Ct
A           22.92         24.21           
B           24.29         22.16           
C           24.29         22.16           
D           27.91         23.76           
E           21.44         22.81           
F           16.50         18.31           
G           17.79         16.56                 
H           17.34         19.09 

In addition, I have measured a standard (STD) curve of copy number of the RNA in question, that I want to use as a reference:
STD_Ct      STD_copies      Log10(STD_copies)
33          4.00E+03        3
28          4.00E+04        4
24          4.00E+05        5
20          4.00E+06        6
15          4.00E+07        7
12          4.00E+08        8


It seems
This the original data form:
Now that we've straightened out the data, it seems like the simplest solution is to just linearly interpolate the copy number from your standard curve.
When I read your standard curve (std) and your sample data (ct) into R, I see that the log10(Ct) fits the copy number fairly well, whereas the linear is a bit harder:

So we can fit a model to predict copy number based on Ct on the STD data:
&gt; fit = lm(std$Log10.STD_copies. ~ std$STD_Ct)
&gt; fit

Call:
lm(formula = std$Log10.STD_copies. ~ std$STD_Ct)

Coefficients:
(Intercept)   std$STD_Ct  
    10.6847      -0.2357  

# we plug those numbers into the linear equation,
# taking the mean of the two replicates for a best estimate.

&gt; rowMeans(ct[,2:3]) * -.2357 + 10.6847
[1] 5.130429 5.210567 5.210567 4.595390 5.469837 6.582341
[7] 6.636553 6.391424


So those are log10(copy number) estimates, of a sort. You can get much more elaborate, of course.