Dear Andrea
I may have not understood the question properly, but I guess it has to do with
replacing values before and after casting.
The molten object ('melting') is a data frame, whilst the cast object ('y') is
an array.
Crucially, the values of the variable "Rep" in the 'melting' data frame become
the names of the columns in each component within the cast array object. So, if
you want to change the values where rep>=1 to 1, you have to do that before
casting the molten object.
If you look at ?cast, you get this example:
> names(airquality) <- tolower(names(airquality))
> aqm <- melt(airquality, id=c("month", "day"), na.rm=TRUE)
> cast(aqm, day ~ month ~ variable)
Let's assign the cast result to an object:
> y=cast(aqm, day ~ month ~ variable)
Now let's have a look at the three objects:
> head(airquality)
ozone solar.r wind temp month day
1 41 190 7.4 67 5 1
2 36 118 8.0 72 5 2
3 12 149 12.6 74 5 3
4 18 313 11.5 62 5 4
5 NA NA 14.3 56 5 5
6 28 NA 14.9 66 5 6
> head(aqm)
month day variable value
1 5 1 ozone 41
2 5 2 ozone 36
3 5 3 ozone 12
4 5 4 ozone 18
5 5 6 ozone 28
6 5 7 ozone 23
> y[1:10,,"ozone"]
month
day 5 6 7 8 9
1 41 NA 135 39 96
2 36 NA 49 9 78
3 12 NA 32 16 73
4 18 NA NA 78 91
5 NA NA 64 35 47
6 28 NA 40 66 32
7 23 29 77 122 20
8 19 NA 97 89 23
9 8 71 97 110 21
10 NA 39 85 NA 24
> y[1:10,,"wind"]
month
day 5 6 7 8 9
1 7.4 8.6 4.1 6.9 6.9
2 8.0 9.7 9.2 13.8 5.1
3 12.6 16.1 9.2 7.4 2.8
4 11.5 9.2 10.9 6.9 4.6
5 14.3 8.6 4.6 7.4 7.4
6 14.9 14.3 10.9 4.6 15.5
7 8.6 9.7 5.1 4.0 10.9
8 13.8 6.9 6.3 10.3 10.3
9 20.1 13.8 5.7 8.0 10.9
10 8.6 11.5 7.4 8.6 9.7
Etc.
So, if you want to change month>5 to 5, you have to do that before casting the
aqm dataframe. Once cast, what you get is an array with (in this example) the
values for the variable month as column names within each component of the
array.
Hope this helps,
José
PS: As an aside, from what I see, there are five Reps (1 to 5), so changing
rep>=1 to 1 will leave you with only 1 category -namely a vector in the arrays.
That's fine but perhaps you meant rep>1 rather than rep>=1?
-----Original Message-----
From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
Behalf Of Andrea Goijman
Sent: 16 January 2013 15:42
To: R help
Subject: [R] Changing frequency values to 1 and 0
Dear list,
I'm working with a large data set, where I grouped several species in one group
(guild). Then I reshaped my data as shown below. Now, I just want to have "Rep"
only as 1 or 0.
I'm not being able to change the values of rep>=1 to 1... tried many things and
I'm not being successful!
> melting=melt(occ.data,id.var=c("guild", "Site", "Rep", "Año"),
measure.var="Pres")
> y=cast(melting, Site ~ Rep ~ guild ~ Año)
Aggregation requires fun.aggregate: length used as default
> y[1:10,,"gui4a",1:2]
, , Año = 2003
Rep
Site 1 2 3 4 5
1021 0 0 0 0 0
1022 0 0 0 0 0
1023 0 0 0 0 0
1024 0 0 0 0 0
1025 0 0 0 0 0
1026 0 0 0 0 0
* 1051 3 1 2 3 5*
* 1052 4 3 5 2 3*
* 1053 4 3 3 3 2*
* 1054 1 2 1 3 0*
, , Año = 2004
Rep
Site 1 2 3 4 5
1021 2 5 5 5 4
1022 6 3 2 2 2
1023 4 1 1 2 2
1024 0 1 2 2 0
1025 0 1 0 1 0
1026 2 1 0 0 1
1051 2 1 3 1 2
1052 2 4 1 1 2
1053 2 4 2 2 1
1054 4 3 3 2 3
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