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1. 1. Normalize the reads by the length of feature, it generate reads per kilobasefeature length. Here length is measured in kilobases but the final TPM values do not depend on the length unit.
      RPK_sf  = X_sf / L_f;
   2. Sum up all the RPKsf in a sample
      PRKObtain a scaling factor for sample s as
      K_s =  ∑  10^-6 ∑^F_f=1 FRPK_sf
   3. Generate a scaling factor for each sample by normalizing the PRK of the sample to the sum PRK of all the samples
      Image Removed,
      where TR is the total reads across all samples
   4. RPK_sf
      
   5. Divide raw reads by the length and the scaling factor to get TPM
      TX_sf = X_sf / L_f  / K_s

• Upper quartile 
• The method is exactly the same as the LIMMA package [7].
  The following is the simple summarization of the calculation:

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