Some Basics Again

When you start R session, It starts in a working directory,. You can manually change it going in File menu. or by the code
>setwd("D:/Rsession")




 


then, you can get the path by command


 




> getwd()


[1] "D:/Rsession"




You can assign values to object by <- or -> sign,





>x<-rnorm(50)


>rnorm(100)->y




if you tried the opposite, you will get error message





> y->rnorm(50)


Error in rnorm(50) <- y : 


  target of assignment expands to non-language object




the objects in your current working directory can be listed by





>objects()






> ls()


[1] "x" "y"




to remove the objects





> rm(x)


> ls()


[1] "y"




to remove all the objects





> rm(list=ls())


> ls()


character(0)




to know the column names of table





> names(xy)


[1] "Rep"      "Genotype" "top"      "root"     "Control" 




to know more information about variables





> ls.str()


xy : 'data.frame':      224 obs. of  5 variables:


 $ Rep     : int  1 1 1 1 1 1 1 1 1 1 ...


 $ Genotype: Factor w/ 28 levels "M1M3","M1S1",..: 10 11 8 9 12 13 14 17 15 16 ...


 $ top     : num  0.65 0.77 0.77 0.73 0.69 0.72 0.56 0.69 0.65 0.86 ...


 $ root    : num  0.48 0.32 0.25 0.31 0.33 0.34 0.28 0.37 0.4 0.3 ...


 $ Control : int  0 0 0 0 0 0 0 0 0 0 ...


y :  num [1:50] -1.824965 -0.400061 -1.241349  2.017474 -0.000123 ...




to access the variable of dataframe





> xy$Rep


  [1] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2


 [38] 2 2 2 2 2 2 2 2 2 2 2 




notice that Rep will not give anything here





> Rep


Error: object "Rep" not found




to make it accessible





> attach(xy)


> Rep


  [1] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2


 [38] 2 2 2 2 2 2 2 2 2 2 2 




to make inaccessible again





> detach()


> Rep


Error: object "Rep" not found




to quit a program




>q() #or


>quit()



 


all for today

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