I have a data.table which is shown below. I want to count combinations of
columns on i and count on j with by. A few examples are given below the
table.
I want to:
all months to show on the output including those that they have zero value
I want the three statements combined in on if possible so the output will
be one data table; that is the outputs are next to each other as manually
illustrated on the last part (desired output).
Thanks--EK
> Test
Color Grade Value Month Day
1: yellow A 20 May 1
2: green B 25 June 2
3: green A 10 April 3
4: black A 17 August 3
5: red C 5 May 5
6: orange D 0 June 13
7: orange E 12 April 5
8: orange F 11 August 8
9: orange F 99 April 23
10: orange F 70 May 7
11: black A 77 June 11
12: green B 87 August 33
13: black A 79 April 9
14: green A 68 May 14
15: black C 90 June 31
16: green D 79 August 11
17: black E 101 April 17
18: red F 90 June 21
19: red F 112 August 13
20: red F 101 April 20
> Test[Color=="green"&Grade=="A", .N, by=Month]
Month N
1: April 1
2: May 1
> Test[Color=="orange"&Grade=="F", .N, by=Month]
Month N
1: August 1
2: April 1
3: May 1
> Test[Color=="orange"&Grade=="F", .N, by=Month]
Month N
1: August 1
2: April 1
3: May 1
> Test[Color=="red"&Grade=="F", .N, by=Month]
Month N
1: June 1
2: August 1
3: April 1
Desired output
N1 N2 N3
April 1 1 1
May 1 1 1
June 0 0 0
August 0 1 1
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