Three values that add to the same number by 0.01 steps

[sunny0]

Hi,

I'd like to create a matrix with three columns so that each element is between 0 and 1 and each row always adds to 1. So, if in the same row the columns are x1, x2, and x3 and x1 =1, then x2 = 0 and x3 = 0. Or if x1 = .03, then x2 = .97 and x3 = 0. Or... x1 = .05, x2 = .01, x3 = .94.

Basically so it accounts for all values of x1,x2,x3 that add up to 1 with the sequence by 0.01.

I tried a nested seq (if that is even possible), but that didn't work.

Is there a way to do this? Perhaps a package that I don't know about?

[arun kirshna]

Hi,
May be this helps:
 set.seed(85)
 mat1 <- matrix(sample(seq(0,1,by=0.01),360000,replace=TRUE),ncol=3)
mat2 <- mat1[sprintf("%.2f",rowSums(mat1))=="1.00",]
 any(!rowSums(mat2))
#[1] FALSE
A.K.


Hi,

I'd like to create a matrix with three columns so that each
element is between 0 and 1 and each row always adds to 1. So, if in the
same row the columns are x1, x2, and x3 and x1 =1, then x2 = 0 and x3 =
0. Or if x1 = .03, then x2 = .97 and x3 = 0. Or... x1 = .05, x2 = .01,
x3 = .94.

Basically so it accounts for all values of x1,x2,x3 that add up to 1 with the sequence by 0.01.

I tried a nested seq (if that is even possible), but that didn't work.

Is there a way to do this? Perhaps a package that I don't know about?

______________________________________________
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[Stephen Ellison]

> I'd like to create a matrix with three columns so that each element is
> between 0 and 1 and each row always adds to 1. So, if in the same row the

You could start with expand.grid

m <- expand.grid(x1=0:100, x2=0:100)  #Avoids comparing floats
m <- m[rowSums(m)<=100,]                    #Throw away the oversized ones
m <- cbind(m, x3=100-rowSums(m))   #Get the final column
m <- m/100                                                     #Scale to [0,1]

table(rowSums(m))  


S Ellison



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[Richard Kwock]

An alternative using runif.

x <- round(runif(10000, 0, 1), 2)
y <- round(runif(10000, 0, 1-x), 2)
z <- round(1-x-y, 2)

sum1 <- cbind(x, y, z)


any(!(sum1[,1] + sum1[,2] + sum1[,3]))


Richard


On Tue, Jan 28, 2014 at 9:36 AM, S Ellison <[hidden email]> wrote:

> > I'd like to create a matrix with three columns so that each element is
> > between 0 and 1 and each row always adds to 1. So, if in the same row the
>
> You could start with expand.grid
>
> m <- expand.grid(x1=0:100, x2=0:100)  #Avoids comparing floats
> m <- m[rowSums(m)<=100,]                    #Throw away the oversized ones
> m <- cbind(m, x3=100-rowSums(m))   #Get the final column
> m <- m/100                                                     #Scale to
> [0,1]
>
> table(rowSums(m))
>
>
> S Ellison
>
>
>
> *******************************************************************
> This email and any attachments are confidential. Any u...{{dropped:13}}

______________________________________________
[hidden email] mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

[arun kirshna]

Also,
library(gtools)
 x <- rdirichlet(1000, c(1,1,1) )
any(!rowSums(x))
#[1] FALSE
A.K.




On Tuesday, January 28, 2014 2:20 PM, Richard Kwock <[hidden email]> wrote:
An alternative using runif.

x <- round(runif(10000, 0, 1), 2)
y <- round(runif(10000, 0, 1-x), 2)
z <- round(1-x-y, 2)

sum1 <- cbind(x, y, z)


any(!(sum1[,1] + sum1[,2] + sum1[,3]))


Richard


On Tue, Jan 28, 2014 at 9:36 AM, S Ellison <[hidden email]> wrote:

> > I'd like to create a matrix with three columns so that each element is
> > between 0 and 1 and each row always adds to 1. So, if in the same row the
>
> You could start with expand.grid
>
> m <- expand.grid(x1=0:100, x2=0:100)  #Avoids comparing floats
> m <- m[rowSums(m)<=100,]                    #Throw away the oversized ones
> m <- cbind(m, x3=100-rowSums(m))   #Get the final column
> m <- m/100                                                     #Scale to
> [0,1]
>
> table(rowSums(m))
>
>
> S Ellison
>
>
>
> *******************************************************************
> This email and any attachments are confidential. Any u...{{dropped:13}}

______________________________________________
[hidden email] mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.


______________________________________________
[hidden email] mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

[sunny0]

Thanks everyone!

I'll give them each a try