Help Function in R

1. Find the detail of a function

?mean

2. Find Package for specific function in R

help.search("mean")

broom::kmeans		kmeans with dplyr and broom	HTML	source
doBy::linest_lsmeans		doBy: Linear estimates and LSmeans	PDF	source	R code
emmeans::AQuickStart		Quick-start guide for emmeans	HTML	source	R code
emmeans::FAQs		FAQs for emmeans	HTML	source	R code
emmeans::interactions		Interaction analysis in emmeans	HTML	source	R code
emmeans::models		Models supported by emmeans	HTML	source
emmeans::predictions		Prediction in emmeans	HTML	source	R code
emmeans::sophisticated		Sophisticated models in emmeans	HTML	source	R code
emmeans::xtending		For developers: Extending emmeans	HTML	source	R code

3. Find documentation for any function in R

help("mean")

4. Find all functions 

apropos("summary")

[1] ".rs.callSummary"         "format.summaryDefault"  
 [3] "print.summary.table"     "print.summary.warnings" 
 [5] "print.summaryDefault"    "summary"                
 [7] "Summary"                 "summary.aov"            
 [9] "summary.connection"      "summary.data.frame"     
[11] "Summary.data.frame"      "summary.Date"           
[13] "Summary.Date"            "summary.default"        
[15] "Summary.difftime"        "summary.factor"         
[17] "Summary.factor"          "summary.glm"            
[19] "summary.lm"              "summary.manova"         
[21] "summary.matrix"          "Summary.numeric_version"
[23] "Summary.ordered"         "summary.POSIXct"        
[25] "Summary.POSIXct"         "summary.POSIXlt"        
[27] "Summary.POSIXlt"         "summary.proc_time"      
[29] "summary.srcfile"         "summary.srcref"         
[31] "summary.stepfun"         "summary.table"          
[33] "summary.warnings"        "summaryRprof"