update imputation page

docs/documentation/imputation.md

@@ -1,15 +1,8 @@
 # Missing value imputation options
 
-Multiple imputation options were provided in FragPipe-Analyst
+Multiple imputation options were provided in FragPipe-Analyst. Perseus-style ** is applied by default for DDA and DIA LFQ data. No imputation is performed for TMT data by default.
 
--   **Perseus-type:** This method is based on popular missing value
-    imputation procedure implemented in *Perseus* software by MaxQuant
-    team. The missing values are replaced by random numbers drawn from a
-    normal distribution of *1.8* standard deviation down shift and with a
-    width of *0.3* of each sample.
--   **bpca:** Bayesian missing value imputation
--   **knn:** Missing values replace by nearest neighbor averaging
-    technique
--   **min:** Replaces the missing values by the smallest non-missing
-    value in the data.
+-   **Perseus-style**: This method is based on popular missing value imputation procedure implemented in *Perseus* software by MaxQuant team. The missing values are replaced by random numbers drawn from a normal distribution of *1.8* standard deviation down shift and with a width of *0.3* of each sample.
+-   **knn:** Missing values replace by nearest neighbor averaging technique
+-   **min:** Replaces the missing values by the smallest non-missing value in the data.
 -   **zero:** Replaces the missing values by **0**.