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