```
# Calculations
# TO DO LIST
# escfish
#
#' Calculate the angle inside the triangle made by the fish's escape path,
#' the line perpendicular to the net boundary, and the net boundary itself.
#' This is necessary for escape time calculations.
#'
#' @param anglevec A vector of angles in radians
#' @return A vector of angles (in radians) relative to the escape path
#' @exmaples
#' adjustangle(3*pi/2)
adjustangle <- function(anglevec){
angle <- anglevec
#0:90* = 0 : pi/2
angle.prime <- angle
# 90*:180* = pi/2 : pi
angle.prime[angle>pi/2 & angle<pi] <- pi - angle[angle>pi/2 & angle<pi]
# 180*:270* = pi : 3pi/2
angle.prime[angle>pi & angle<3*pi/2] <- angle[angle>pi & angle<3*pi/2] - pi
# 270*:360 = 3pi/2 : 2pi
angle.prime[angle>3*pi/2] <- 2*pi - angle[angle>3*pi/2]
return(angle.prime)
}
#' Summarizes the proportion of fish caught.
#' @param fish A data.frame of fish information, created by mkfish and modifed by escfish.
#' @param pop A data.frame of tow information, created by mktow.
#' @param n.fish Numeric. Tumber of fish to place in the path of the gear for each population.
#' @return Returns a data.frame of pop with catch and catch.p appended to it
#' @examples
#' escfish(fish3, tow3, n.fish = 1000)
sumcatch <- function(fish, pop, n.fish){
catch <- summaryBy(caught ~ pop, data = fish, FUN = sum)[,2]
catch.p <- catch/n.fish
return(cbind(pop, catch, catch.p))
}
#' Calculates which fish escape the net.
#'
#' @param fish A data.frame of fish information, created by mkfish
#' @param pop A data.frame of tow information, created by mktow
#' @param swim.fail Numeric [0, 1]. Proportion of fish that fail to swim.
#' @return Returns the original fish data.frame with new columns for
#' pop values, fish position, and caught status
#' @examples
#' escfish(fish3, tow3)
escfish <- function(fish, pop, swim.fail = 0.4,
width.path, height.path = width.path){
fish2 <- merge(fish, pop,
by = "pop",
all.x = TRUE)
# calculate the angle inside the triangle made by the fish's escape path,
# the line perpendicular to the net boundary, and the net boundary itself
fish2$angle.prime <- adjustangle(fish2$angle)
# Define parameters:
y <- fish2$distance
z <- fish2$height
turn <- fish2$angle.prime
pitch <- fish2$angle.pitch
# Parameters to calculate:
# x = distance the fish travels relative to the movement direction of the net
# x > 0 ==> moving away from the net; x < 0 ==> moving toward the net
# w = distance traveled by the fish (swimming distance to escape);
# also the hypotenuse of the triangle on the turned vertical plane
# u = hypotenuse of the triangle on the horizontal plane
# s = distance the fish travels in the vertical direction to the edge of the net
# Assume fish escape out the side of the path of the net:
# Calculate the sides of the triangle on the horizontal plane:
u <- y * cos(turn)
x <- y * tan(turn)
# Calculate the sides of the triangle on the turned vertical plane:
w <- u / sin(pitch)
#s <- u / tan(pitch)
# Assume the fish escapes out the bottom of the path of the net:
wb <- z / cos(pitch)
ub <- tan(pitch) / z
xb <- ub * sin(turn)
# Does the fish escape to the side or the bottom?
side <- (u > y)
fish2 <- cbind(fish2, x, w, side)
# fish2$u[which(side == FALSE)] <- ub[which(side == FALSE)]
fish2$x[which(side == FALSE)] <- xb[which(side == FALSE)]
fish2$w[which(side == FALSE)] <- wb[which(side == FALSE)]
names(fish2)[12:14] <- c("x.dist", "swim.dist", "side")
# How long goes it take the fish to swim to safety?
fish2$esc.time <- fish2$swim.dist / fish2$fish.vel
# Where is the net when the fish escapes?
fish2$net.pos <- fish2$esc.time * fish2$net.vel
# The fish is caught if the net has moved past its escape position at the time when it reaches
# the edge of the path of the net
fish2$caught <- as.numeric(fish2$net.pos > (fish2$rxn.dist + fish2$x.dist))
return(fish2)
}
#
# test1 <- escfish2(fish3, tow3,
# width.path = width.path,
# height.path = width.path)
# names(test1)
```

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