Thanks for your answers Arun. Unfortunately the code didn't work and I am getting the error: arguments must have same length. Here are sample input and output:
INPUT:
Vehicle ID Vehicle Class Vehicle Length Vehicle Width
2 2 13.5 4.5
2 2 13.5 4.5
2 2 13.5 4.5
2 2 13.5 4.5
3 2 13.5 4.0
3 2 13.5 4.0
3 2 13.5 4.0
3 2 13.5 4.0
4 2 10.0 4.5
4 2 10.0 4.5
4 2 10.0 4.5
4 2 10.0 4.5
5 3 23.0 4.5
5 3 23.0 4.5
5 3 23.0 4.5
5 3 23.0 4.5
6 3 76.5 4.5
6 3 76.5 4.5
6 3 76.5 4.5
6 3 76.5 4.5
6 3 76.5 4.5
7 1 10.0 3.0
7 1 10.0 3.0
7 1 10.0 3.0
7 1 10.0 3.0
8 2 13.5 5.5
8 2 13.5 5.5
8 2 13.5 5.5
8 2 13.5 5.5Note that in this input: Total number of cars=4, trucks=2, motorcycles=1
Sample OutputGroup: cars
VehicleLength VehicleWidth Proportion
13.5 4.5 0.25
13.5 4.0 0.25
13.5 5.5 0.25
23.0 4.5 0.25

Group:trucks
VehicleLength VehicleWidth Proportion
23.0 4.5 0.5
76.0 4.5 0.5

Group: motorcycles
VehicleLength VehicleWidth Proportion
10.0 3.0 1.0

Umair Durrani

email: umairdurrani@outlook.com


> Date: Sat, 30 Nov 2013 23:41:28 -0800
> From: smartpink111@yahoo.com
> Subject: Re: [R] How to get the proportions of data with respect to two variables in R?
> To: r-help@r-project.org
> CC: umairdurrani@outlook.com
> 
> Hi,
> It is better to provide a reproducible example.
> May be this helps:
> set.seed(252)
> dat1 <- data.frame(`Vehicle ID`=sample(150,150,replace=FALSE),`Vehicle Class`=rep(1:4,c(20,40,30,60)), `Vehicle length`= sample(15:25,150,replace=TRUE), `Vehicle width`= sample(4:10,150,replace=TRUE),check.names=FALSE)
> cars <- subset(dat1,`Vehicle Class`==2)
>  by(cars,INDICES=cars$`Vehicle length`,FUN=table(cars$`Vehicle width`))  
> #Error in FUN(X[[1L]], ...) : could not find function "FUN"
> 
> by(cars$`Vehicle width`,INDICES=cars$`Vehicle length`, table)
>  by(dat1$`Vehicle width`,list(dat1$`Vehicle Class`,dat1$`Vehicle length`), table)
> 
> 
> #Also, you may check
> 
> ftable(dat1[2:4])
> prop.table(ftable(dat1[2:4]),1)
> 
> 
> A.K.
> 
> 
> 
> 
> 
> On Sunday, December 1, 2013 12:08 AM, umair durrani <umairdurrani@outlook.com> wrote:
> I have 4 columns: Vehicle ID, Vehicle Class, Vehicle Length and Vehicle Width. Every vehicle has a unique vehicle ID (e.g. 2, 4, 5,...) and the data was collected every 0.1 seconds which means that vehicle IDs are repeated in Vehicle ID column for the number of times they were observed. There are three vehicle classes i.e. 1=motorcycles, 2=cars, 3=trucks in the Vehicle Class column and the lengths and widths are in their respective columns against every vehicle ID. I want to subset the data by vehicle class and then find the proportions of each vehicle model (unique length and width) within every class. For example, for the Vehicle Class = 2 i.e. car, I want to find different models of cars (unique length and width) and their proportions with respect to total number of cars. Here is what I have done so far:To subset data by Vehicle Classcars <- subset(b, b$'Vehicle class'==2)
> trucks <- subset(b, b$'Vehicle class'==3)
> motorcycles <- subset(b, b$'Vehicle class'==1)To find the number of carsnumofcars <- length(unique(cars$'Vehicle ID')) # 2830
> numoftrucks <- length(unique(trucks$'Vehicle ID')) # 137
> numofmotorcycles <- length(unique(motorcycles$'Vehicle ID'))# 45The above code worked but I could not find the proportions by using the code below:by (cars, INDICES=cars$'Vehicle Length', FUN=table(class$'Vehicle width'))R gives an error stating that it could not find 'FUN'. Please help me in finding the proportions of each model within all classes of vehicles.
> 
> Umair Durrani
> 
> email: umairdurrani@outlook.com
>                           
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> 
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