thr3ads.net - R help - [R] for loop not working [Oct 2015]

If this information is useful, please help other people find it:
Share via:

mnw

2015-Oct-09 15:08 UTC

[R] for loop not working

Hi. I have some code which loops through raw GPS data. This initial loop
calculates distance, angle, speed etc between successive coordinates as well
as type of movement e.g.left, right, forward. I want to construct a second
loop that goes through the movements and records 'Changes' as either
'0' or
'1' depending on whether the movement changed or not. I have put the
whole
code in for reference but the additional loop begins at the object
'holder.'
I want to store movements in holder and then loop through holder to
determine 'changes.' At the moment it gives me 'Error in holder[[t -
1]] :
attempt to select less than one element.' The moment i make holder [[t]] it
works but just gives a list of '0's. I have tried many different things
and
just cannot get it to work, so any help would be very much appreciated.
Again, sorry for the long post.




lst <- list() # temporary list to store the results
for (i in seq(1, nrow(R) - 1)){ # loop through each row of the 'R'
matrix
  lat1 <- deg2rad(R[i, 4])
  long1 <- deg2rad(R[i, 5])
  lat2 <- deg2rad(R[i + 1, 4])
  long2 <- deg2rad(R[i + 1, 5])
  gcd_vif <- gcd.vif(lat1, long1, lat2, long2)
  
  # calc estimated speed by mean of speeds between two GPS records
  estSpeed <- (R[i, 6] + R[i+1, 6])/2
  
  # calculate acceleration (velocity)
  accel <- (R[i+1, 6] - R[i, 6]) / GPSSample
  
  # calculate absolute heading 
  heading <- absoluteHeading(lat1, long1, lat2, long2)

  # calculate bearing relative to previous GPS record
  relAngle <- 0
  # if the number of GPS records is less than 3 then no change in track
  if (i < 1) relAngle = heading
  # otherwise consider the previous heading in order to calculate the new
track
  else if (i > 0) {
    relAngle = (previousHeading - heading)
  
  }

  
  # determine whether movement is occurring and if so what type
  # if there are insufficient history items then just record movement types
discretely
   if (i < historyLength) movement <- movementType(relAngle,
angleThreshold)
  
  else if (i > historyLength-1) {
    # Array to store speeds
    speedHistory <- array(historyLength)
    n = historyLength-1
    # get the speeds from the previous n (hisoryLength) "Movements" 
    for (j in seq(1, length(historyLength))){
      speedHistory [n] = R[i-j, 6]
      n-1
      }
      
      if (!bayesFilter(speedHistory, minSpeed, GPS_accy)) movement <-
"non-moving" 
      else if(bayesFilter(speedHistory, minSpeed, GPS_accy)) movement <-
movementType(relAngle, angleThreshold)
  
   
  }
  
  
  holder <- list(movement)
  holder [[i]] <- (movement)
  
  
  for (t in length(holder)){
    if (holder[[t]] == holder[[t-1]]) 
      changes <- 0
    else changes <- 1
    
  }
    
  
    
  # update previous heading information
  previousHeading = heading
 





  # Store the input data and the results
  lst[[i]] <- c(
    latitude_position_1 = lat1, 
    longtude_position_1 = long1, 
    latitude_position_2 = lat2, 
    longtude_position_2 = long2, 
    Distance = gcd_vif,
    Speed = estSpeed,
    Acceleration = accel,
    Absolute_Heading = heading,
    Relative_Heading = relAngle,
    Movement = movement,
    Changes = changes
  
  )
  
}  
Results <- as.data.frame(do.call(rbind, lst)) # store the input data and the
results in a data frame
Results



--
View this message in context:
http://r.789695.n4.nabble.com/for-loop-not-working-tp4713392.html
Sent from the R help mailing list archive at Nabble.com.

Jim Lemon

2015-Oct-10 11:03 UTC

head link

[R] for loop not working

Hi mnw,
It looks to me as though you are testing the entire "holder" list each
time
you go through the function. First, I'm not sure that a simple
"==" is the
test you want. "movement" seems to be more than a single value and so
you
might want to write a function that tests whether all of the components of
two "movement" objects are equal e.g.:

move_change<-function(currentx,previousx) {
 if(currentx$speed == previousx$speed) {
  if(currentx$heading == previousx$heading) return(0)
 }
 return(1)
}

Second, you probably don't want to test the entire list each time you loop
through the function. Just use:

 if(i > 1) changes<-move_change(movement,holder)
 holder<-movement

Jim


On Sat, Oct 10, 2015 at 2:08 AM, mnw <maw90 at aber.ac.uk> wrote:
> Hi. I have some code which loops through raw GPS data. This initial loop
> calculates distance, angle, speed etc between successive coordinates as
> well
> as type of movement e.g.left, right, forward. I want to construct a second
> loop that goes through the movements and records 'Changes' as
either '0' or
> '1' depending on whether the movement changed or not. I have put
the whole
> code in for reference but the additional loop begins at the object
> 'holder.'
> I want to store movements in holder and then loop through holder to
> determine 'changes.' At the moment it gives me 'Error in
holder[[t - 1]] :
> attempt to select less than one element.' The moment i make holder
[[t]] it
> works but just gives a list of '0's. I have tried many different
things and
> just cannot get it to work, so any help would be very much appreciated.
> Again, sorry for the long post.
>
>
>
>
> lst <- list() # temporary list to store the results
> for (i in seq(1, nrow(R) - 1)){ # loop through each row of the 'R'
matrix
>   lat1 <- deg2rad(R[i, 4])
>   long1 <- deg2rad(R[i, 5])
>   lat2 <- deg2rad(R[i + 1, 4])
>   long2 <- deg2rad(R[i + 1, 5])
>   gcd_vif <- gcd.vif(lat1, long1, lat2, long2)
>
>   # calc estimated speed by mean of speeds between two GPS records
>   estSpeed <- (R[i, 6] + R[i+1, 6])/2
>
>   # calculate acceleration (velocity)
>   accel <- (R[i+1, 6] - R[i, 6]) / GPSSample
>
>   # calculate absolute heading
>   heading <- absoluteHeading(lat1, long1, lat2, long2)
>
>   # calculate bearing relative to previous GPS record
>   relAngle <- 0
>   # if the number of GPS records is less than 3 then no change in track
>   if (i < 1) relAngle = heading
>   # otherwise consider the previous heading in order to calculate the new
> track
>   else if (i > 0) {
>     relAngle = (previousHeading - heading)
>
>   }
>
>
>   # determine whether movement is occurring and if so what type
>   # if there are insufficient history items then just record movement types
> discretely
>    if (i < historyLength) movement <- movementType(relAngle,
> angleThreshold)
>
>   else if (i > historyLength-1) {
>     # Array to store speeds
>     speedHistory <- array(historyLength)
>     n = historyLength-1
>     # get the speeds from the previous n (hisoryLength)
"Movements"
>     for (j in seq(1, length(historyLength))){
>       speedHistory [n] = R[i-j, 6]
>       n-1
>       }
>
>       if (!bayesFilter(speedHistory, minSpeed, GPS_accy)) movement <-
> "non-moving"
>       else if(bayesFilter(speedHistory, minSpeed, GPS_accy)) movement <-
> movementType(relAngle, angleThreshold)
>
>
>   }
>
>
>   holder <- list(movement)
>   holder [[i]] <- (movement)
>
>
>   for (t in length(holder)){
>     if (holder[[t]] == holder[[t-1]])
>       changes <- 0
>     else changes <- 1
>
>   }
>
>
>
>   # update previous heading information
>   previousHeading = heading
>
>
>
>
>
>
>   # Store the input data and the results
>   lst[[i]] <- c(
>     latitude_position_1 = lat1,
>     longtude_position_1 = long1,
>     latitude_position_2 = lat2,
>     longtude_position_2 = long2,
>     Distance = gcd_vif,
>     Speed = estSpeed,
>     Acceleration = accel,
>     Absolute_Heading = heading,
>     Relative_Heading = relAngle,
>     Movement = movement,
>     Changes = changes
>
>   )
>
> }
> Results <- as.data.frame(do.call(rbind, lst)) # store the input data and
> the
> results in a data frame
> Results
>
>
>
> --
> View this message in context:
> http://r.789695.n4.nabble.com/for-loop-not-working-tp4713392.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> 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.
>
	[[alternative HTML version deleted]]

David L Carlson

2015-Oct-10 18:00 UTC

head link

[R] for loop not working

In addition to Jim's comments you would benefit by learning more about how R
works. You are using loops for operations that could easily be vectorized. It is
not clear where your functions are coming from (eg. deg2rad and gcd.vif) but
package geosphere will get your distances and bearings directly without looping.
> install.packages("geosphere")
> library(geosphere)
> Cities <- c("New York", "Miami", "Los
Angeles", "Seattle", "Chicago")
> Lat <- c(40.7127, 25.7753, 34.05, 47.6097, 41.8369)
> Long <- c(-74.0059, -80.2089, -118.250, -122.3331, -87.6847)
> Places <- data.frame(Cities, Lat, Long)
> Places       Cities     Lat      Long
1    New York 40.7127  -74.0059
2       Miami 25.7753  -80.2089
3 Los Angeles 34.0500 -118.2500
4     Seattle 47.6097 -122.3331
5     Chicago 41.8369  -87.6847> n <- nrow(Places)
> distVincentyEllipsoid(Places[1:(n-1), 3:2], Places[2:n, 3:2])
[1] 1753420 3763369 1544119 2794013> bearing(Places[1:(n-1), 3:2], Places[2:n, 3:2])[1] -158.98140  -66.71221  -11.57217   90.36231


David L. Carlson
Department of Anthropology
Texas A&M University

-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Jim Lemon
Sent: Saturday, October 10, 2015 6:04 AM
To: mnw <maw90 at aber.ac.uk>
Cc: r-help mailing list <r-help at r-project.org>
Subject: Re: [R] for loop not working

Hi mnw,
It looks to me as though you are testing the entire "holder" list each
time
you go through the function. First, I'm not sure that a simple
"==" is the
test you want. "movement" seems to be more than a single value and so
you
might want to write a function that tests whether all of the components of
two "movement" objects are equal e.g.:

move_change<-function(currentx,previousx) {
 if(currentx$speed == previousx$speed) {
  if(currentx$heading == previousx$heading) return(0)
 }
 return(1)
}

Second, you probably don't want to test the entire list each time you loop
through the function. Just use:

 if(i > 1) changes<-move_change(movement,holder)
 holder<-movement

Jim


On Sat, Oct 10, 2015 at 2:08 AM, mnw <maw90 at aber.ac.uk> wrote:
> Hi. I have some code which loops through raw GPS data. This initial loop
> calculates distance, angle, speed etc between successive coordinates as
> well
> as type of movement e.g.left, right, forward. I want to construct a second
> loop that goes through the movements and records 'Changes' as
either '0' or
> '1' depending on whether the movement changed or not. I have put
the whole
> code in for reference but the additional loop begins at the object
> 'holder.'
> I want to store movements in holder and then loop through holder to
> determine 'changes.' At the moment it gives me 'Error in
holder[[t - 1]] :
> attempt to select less than one element.' The moment i make holder
[[t]] it
> works but just gives a list of '0's. I have tried many different
things and
> just cannot get it to work, so any help would be very much appreciated.
> Again, sorry for the long post.
>
>
>
>
> lst <- list() # temporary list to store the results
> for (i in seq(1, nrow(R) - 1)){ # loop through each row of the 'R'
matrix
>   lat1 <- deg2rad(R[i, 4])
>   long1 <- deg2rad(R[i, 5])
>   lat2 <- deg2rad(R[i + 1, 4])
>   long2 <- deg2rad(R[i + 1, 5])
>   gcd_vif <- gcd.vif(lat1, long1, lat2, long2)
>
>   # calc estimated speed by mean of speeds between two GPS records
>   estSpeed <- (R[i, 6] + R[i+1, 6])/2
>
>   # calculate acceleration (velocity)
>   accel <- (R[i+1, 6] - R[i, 6]) / GPSSample
>
>   # calculate absolute heading
>   heading <- absoluteHeading(lat1, long1, lat2, long2)
>
>   # calculate bearing relative to previous GPS record
>   relAngle <- 0
>   # if the number of GPS records is less than 3 then no change in track
>   if (i < 1) relAngle = heading
>   # otherwise consider the previous heading in order to calculate the new
> track
>   else if (i > 0) {
>     relAngle = (previousHeading - heading)
>
>   }
>
>
>   # determine whether movement is occurring and if so what type
>   # if there are insufficient history items then just record movement types
> discretely
>    if (i < historyLength) movement <- movementType(relAngle,
> angleThreshold)
>
>   else if (i > historyLength-1) {
>     # Array to store speeds
>     speedHistory <- array(historyLength)
>     n = historyLength-1
>     # get the speeds from the previous n (hisoryLength)
"Movements"
>     for (j in seq(1, length(historyLength))){
>       speedHistory [n] = R[i-j, 6]
>       n-1
>       }
>
>       if (!bayesFilter(speedHistory, minSpeed, GPS_accy)) movement <-
> "non-moving"
>       else if(bayesFilter(speedHistory, minSpeed, GPS_accy)) movement <-
> movementType(relAngle, angleThreshold)
>
>
>   }
>
>
>   holder <- list(movement)
>   holder [[i]] <- (movement)
>
>
>   for (t in length(holder)){
>     if (holder[[t]] == holder[[t-1]])
>       changes <- 0
>     else changes <- 1
>
>   }
>
>
>
>   # update previous heading information
>   previousHeading = heading
>
>
>
>
>
>
>   # Store the input data and the results
>   lst[[i]] <- c(
>     latitude_position_1 = lat1,
>     longtude_position_1 = long1,
>     latitude_position_2 = lat2,
>     longtude_position_2 = long2,
>     Distance = gcd_vif,
>     Speed = estSpeed,
>     Acceleration = accel,
>     Absolute_Heading = heading,
>     Relative_Heading = relAngle,
>     Movement = movement,
>     Changes = changes
>
>   )
>
> }
> Results <- as.data.frame(do.call(rbind, lst)) # store the input data and
> the
> results in a data frame
> Results
>
>
>
> --
> View this message in context:
> http://r.789695.n4.nabble.com/for-loop-not-working-tp4713392.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> 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.
>
	[[alternative HTML version deleted]]

______________________________________________
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.

mnw

2015-Oct-13 09:35 UTC

head link

[R] for loop not working

Thank you for your comments. I guess what I need is to store movements and
then loop through that matrix. Here is a snippet of the 'movement' code.
I
am trying to fill the matrix below with data from this loop. Is there
something else my matrix (bottom) requires? Or its positioning?

Many thanks,







# determine whether movement is occurring and if so what type
  # if there are insufficient history items then just record movement types
discretely
  
   if (i < historyLength) movement <- movementType(relAngle,
angleThreshold)
  
  else if (i > historyLength-1) {
    # Array to store speeds
    speedHistory <- array(historyLength)
    n = historyLength-1
    # get the speeds from the previous n (hisoryLength) "Movements" 
    for (j in seq(1, length(historyLength))){
      speedHistory [n] = R[i-j, 6]
      n-1
      }
    
      if (!bayesFilter(speedHistory, minSpeed, GPS_accy)) movement <-
"non-moving" 
      else if(bayesFilter(speedHistory, minSpeed, GPS_accy)) movement <-
movementType(relAngle, angleThreshold)
  
  
    
    holder <- matrix(data = movement, nrow = nrow(R), ncol = 1)
   
    
  }
  



--
View this message in context:
http://r.789695.n4.nabble.com/for-loop-not-working-tp4713392p4713525.html
Sent from the R help mailing list archive at Nabble.com.

R help - Oct 2015 - for loop not working

[R] for loop not working

[R] for loop not working

[R] for loop not working

[R] for loop not working