+ signs appearing in console in R

Answer 09/07/2018 Developer FAQ 1

I´m quite new at programming, and I started with R. I wanted to make a script which takes as input a matrix with the columns: time, x, y (coordenates) and then divide the time spent in each quadrant of a circular area. I have a roughly done script, but for any reason I don´t understand, when I execute the for loop in the editor, it appears all the letters red in the console with a "+" at the beginning of each line, which doesn´t let me open any other object any more when I call it.

set.seed(20)
x = matrix(rnorm(10,3,4),10,1)
y = matrix (rnorm(10,3,4),10,1)
time = matrix (1:10,10,1)
a = cbind (time,x,y)
colnames(a) = c("time","x","y")


  upperright =  a[,2] > 0 && a[,3] > 0 
  upperleft =   a[,2] < 0 && a[,3] > 0
  lowerright =  a[,2] > 0 && a[,3] < 0
  lowerleft =   a[,2] < 0 && a[,3] < 0

calculation <- function () {
    upperrightquadrant = 0
    upperleftquadrant = 0
    lowerrightquadrant = 0
    lowerleftquadrant = 0
for (i in c(1:nrow(a))){
    if (upperright) upperrightquadrant <<- sum((a[i,1]-a[i-1,1]))
    if (upperleft)upperleftquadrant <<- sum((a[i,1]-a[i-1,1]))
    if (lowerright) lowerrightquadrant <<-sum((a[i,1]-a[i-1,1]))
    if (lowerleft) lowerleftquadrant <<- sum((a[i,1]-a[i-1,1]))
}}
output = lapply (a, calculation)

Answer1:

The + symbols are only a way to show that the current statement is conitnuation of the previous lines's statement. That's perfectly OK. There are a couple of other problems with your program which are stopping it from producing your intended result. If I have in fact, understood what you are trying to do, I have added a possible solution at the end. First, let me suggest the edits and the reason for them:

<ol> <li>& should have been used instead of &&. & is the vectorized operator. So, upperright = a[,2] > 0 & a[,3] > 0 instead of upperright = a[,2] > 0 && a[,3] > 0.</li> <li>You are passing a value to the function so its definition should include the parameter calculation <- function (a) instead of calculation <- function ().</li> <li>upperright, upperleft, ... are vectors and you should check individual elements instead of the whole vector if (upperright[i]) instead of if (upperright).</li> <li>Problem with sum((a[i,1]-a[i-1,1])) at i==1, i-1 equals 0. If you are only counting, incrementing the count by 1 should be sufficient.</li> <li>The objects upperrightquadrant, upperleftquadrant, ... are in your function environment only. So, no need for <<-.</li> <li>

Finally, as you have already written the for loop to iterate over your matrix rowwise, no need for lapply or other similar looping functions.

Only a suggestion: Use <- operator for assignments instead of =.

</li> </ol>

Now, the corrected program:

set.seed(20)
x = matrix(rnorm(10,3,4),10,1)
y = matrix (rnorm(10,3,4),10,1)
time = matrix (1:10,10,1)
a = cbind (time,x,y)

colnames(a) = c("time","x","y")

upperright =  a[,2] > 0 & a[,3] > 0 
upperleft =   a[,2] < 0 & a[,3] > 0
lowerright =  a[,2] > 0 & a[,3] < 0
lowerleft =   a[,2] < 0 & a[,3] < 0

calculation <- function (a) {
  upperrightquadrant = 0
  upperleftquadrant = 0
  lowerrightquadrant = 0
  lowerleftquadrant = 0
  for (i in c(1:nrow(a))){
    if (upperright[i]) upperrightquadrant <- upperrightquadrant + 1
    if (upperleft[i]) upperleftquadrant <- upperleftquadrant + 1
    if (lowerright[i]) lowerrightquadrant <- lowerrightquadrant + 1
    if (lowerleft[i]) lowerleftquadrant <- lowerleftquadrant + 1
  }

  list(upperrightquadrant = upperrightquadrant, upperleftquadrant = upperleftquadrant,
       lowerrightquadrant = lowerrightquadrant, lowerleftquadrant = lowerleftquadrant)
}
output = calculation(a)

print(a)        # input
print(output)   # output

EDIT

This is the edit for what you requested (Case where time instances are not contiguous). Just replace the for loop with this one:

  for (i in c(1:nrow(a))){
    if(i>1){
      if (upperright[i]) upperrightquadrant <- upperrightquadrant + a[i, 1] - a[i-1, 1]
      if (upperleft[i]) upperleftquadrant <- upperleftquadrant + a[i, 1] - a[i-1, 1]
      if (lowerright[i]) lowerrightquadrant <- lowerrightquadrant + a[i, 1] - a[i-1, 1]
      if (lowerleft[i]) lowerleftquadrant <- lowerleftquadrant + a[i, 1] - a[i-1, 1]
    } else {
      if (upperright[i]) upperrightquadrant <- upperrightquadrant + a[i, 1]
      if (upperleft[i]) upperleftquadrant <- upperleftquadrant + a[i, 1]
      if (lowerright[i]) lowerrightquadrant <- lowerrightquadrant + a[i, 1]
      if (lowerleft[i]) lowerleftquadrant <- lowerleftquadrant + a[i, 1]
    }
  }

Hope, this helps.