Sorting descending or ascending a column based on another column in R

Lets start with typical sorting. Sorting a table in R is fairly straight forward.

sample data (tbl)

ID	SUB ID	Value
A	sub_3	55.28
C	sub_3	55.89
A	sub_3	56.61
B	sub_3	56.67
A	sub_3	59.01
C	sub_3	63.71
C	sub_4	41.06
D	sub_4	42.43
C	sub_4	43.07
A	sub_4	43.29
D	sub_4	53.56
C	sub_4	53.61
C	sub_4	53.93
D	sub_4	55.06
D	sub_4	55.62
B	sub_5	54.9
B	sub_5	55.92
B	sub_5	55.94
D	sub_5	56.78
C	sub_5	56.91
D	sub_5	59.65
B	sub_5	60.01
C	sub_6	35.08
D	sub_6	37.03
D	sub_6	40.97
C	sub_6	41.68
C	sub_6	43.49
D	sub_6	45.92

Lets sort by column 'Value'.

Attach the table.
> attach(tbl)


Then sort, here i create another table tbl1
> tbl1 <- tbl[order( Value),]


You will get a ascending order 'Value'

If we want Decending order then the code will be,

> tbl1 <- tbl[order( -Value),]

Now  there is a need to sort the 'Value' Ascending when the SUB.ID is odd and descending when the SUB.ID is even.

To do this we need to new column, 'S_Value'

For SUB.IDs sub_4 and sub_4 change the 'Value' to negative. 

> tbl$S_Value <- ifelse((tbl$SUB.ID == 'sub_4' | tbl$SUB.ID == 'sub_6') , -tbl$Value, tbl$Value)

R Operators

https://www.statmethods.net/management/operators.html

Attach again
> attach(tbl)


Now sort by two columns

>  tbl3 <- tbl[order(SUB.ID, S_Value),]

We will get what we want..

That's it.