Hii, 

I was working on this microRNA expression analysis. while doing I stuck by this error. Need to help to proceed further

Thank you

>library(affy)
>data <- ReadAffy() 
>data
AffyBatch object
size of arrays=541x541 features (18 kb)
cdf=miRNA-4_0 (??? affyids)
number of samples=4
Error in getCdfInfo(object) : 
  Could not obtain CDF environment, problems encountered:
Specified environment does not contain miRNA-4_0
Library - package mirna40cdf not installed
Bioconductor - mirna40cdf not available
In addition: Warning message:
missing cdf environment! in show(AffyBatch) 

I have searched to find solution for the cdf file.How to obtain a CDF 

You cannot use the affy/makecdfenv pipeline with these arrays. You should be using oligo instead.

library(oligo)
dat <- read.celfiles(list.celfiles())
eset <- rma(dat)

This basically means that the CDF package to work with this microarray is not available in Bioconductor. If you do have the CDF file yourself (usually you can find them at Affymetrix) you could try to create the package by yourself using the makecdfenv package, install it and then you should be able to process these arrays.