R help - Dec 2015 - Converting from Continuous 2D Points to Continuous 2D Vectors

Greetings!

I have a fairly large dataframe (df) with pathing information in the form of
continuous x,y coordinates:

df$x
df$y

With these data, I would like to:
1. Calculate a set of continuous vectors
2. Determine the angle between each of these vectors (in degrees)
3. Count the number of angles in the dataframe that meet a certain threshold
(i.e. <90?)

Here's what I've come up with so far:

### Function that calculates the angle between two vectors in 2D space:

angle <- function(x,y){ # x and y are vectors
  dot.prod <- x%*%y 
  norm.x <- norm(x,type="2")
  norm.y <- norm(y,type="2")
  theta <- acos(dot.prod / (norm.x * norm.y))
  (180*as.numeric(theta))/pi # returns the angle in degrees
}

### Test the function:
x <- as.matrix(c(2,1))
y <- as.matrix(c(1,2))
angle(t(x),y)
[1] 36.8699

Thank you!

Ok. And what is the problem now?

B.



On Dec 17, 2015, at 4:25 PM, Sidoti, Salvatore A. <sidoti.23 at
buckeyemail.osu.edu> wrote:
> Greetings!
> 
> I have a fairly large dataframe (df) with pathing information in the form
of continuous x,y coordinates:
> 
> df$x
> df$y
> 
> With these data, I would like to:
> 1. Calculate a set of continuous vectors
> 2. Determine the angle between each of these vectors (in degrees)
> 3. Count the number of angles in the dataframe that meet a certain
threshold (i.e. <90?)
> 
> Here's what I've come up with so far:
> 
> ### Function that calculates the angle between two vectors in 2D space:
> 
> angle <- function(x,y){ # x and y are vectors
>  dot.prod <- x%*%y 
>  norm.x <- norm(x,type="2")
>  norm.y <- norm(y,type="2")
>  theta <- acos(dot.prod / (norm.x * norm.y))
>  (180*as.numeric(theta))/pi # returns the angle in degrees
> }
> 
> ### Test the function:
> x <- as.matrix(c(2,1))
> y <- as.matrix(c(1,2))
> angle(t(x),y)
> [1] 36.8699
> 
> Thank you!
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> 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.

Look at the CRAN Task View: "Handling and Analyzing Spatio-Temporal
Data," particularly the section on "Moving objects,
trajectories." The tools you need are probably already available.

https://cran.r-project.org/web/views/SpatioTemporal.html

-------------------------------------
David L Carlson
Department of Anthropology
Texas A&M University
College Station, TX 77840-4352

-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Sidoti,
Salvatore A.
Sent: Thursday, December 17, 2015 3:25 PM
To: r-help at r-project.org
Subject: [R] Converting from Continuous 2D Points to Continuous 2D Vectors

Greetings!

I have a fairly large dataframe (df) with pathing information in the form of
continuous x,y coordinates:

df$x
df$y

With these data, I would like to:
1. Calculate a set of continuous vectors
2. Determine the angle between each of these vectors (in degrees)
3. Count the number of angles in the dataframe that meet a certain threshold
(i.e. <90?)

Here's what I've come up with so far:

### Function that calculates the angle between two vectors in 2D space:

angle <- function(x,y){ # x and y are vectors
  dot.prod <- x%*%y 
  norm.x <- norm(x,type="2")
  norm.y <- norm(y,type="2")
  theta <- acos(dot.prod / (norm.x * norm.y))
  (180*as.numeric(theta))/pi # returns the angle in degrees
}

### Test the function:
x <- as.matrix(c(2,1))
y <- as.matrix(c(1,2))
angle(t(x),y)
[1] 36.8699

Thank you!
______________________________________________
R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
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.