fixed a bug in critical_depth and updated to address CRAN comments.

DESCRIPTION

@@ -1,11 +1,14 @@
 Package: rivr
 Type: Package
-Title: Steady and unsteady open channel flow computation
+Title: Steady and Unsteady Open-Channel Flow Computation
 Version: 0.9.1
 Date: 2015-01-10
 Author: Michael C Koohafkan [aut, cre]
 Maintainer: Michael C Koohafkan <michael.koohafkan@gmail.com>
-Description: A tool for undergraduate courses in open channel hydraulics. Provides functions for computing normal and critical depths, steady-state water surface profiles (e.g. backwater curves) and unsteady flow computations (e.g. flood wave routing).
+Description: A tool for undergraduate courses in open-channel hydraulics. 
+    Provides functions for computing normal and critical depths, steady-state 
+    water surface profiles (e.g. backwater curves) and unsteady flow 
+    computations (e.g. flood wave routing).
 URL: https://github.com/mkoohafkan/rivr 
 BugReports: https://github.com/mkoohafkan/rivr/issues 
 License: GPL (>= 3) + file LICENSE

R/RcppExports.R

@@ -105,8 +105,8 @@ normal_depth <- function(So, n, Q, yopt, Cm, B, SS) {
 #' @param SS Channel sideslope [\eqn{L L^{-1}}].
 #' @return The critical depth \eqn{y_c} [\eqn{L}].
 #' @examples
-#' critical_depth(250, 32.2, 2, 100, 0) # rectangular channel
-#' critical_depth(126, 9.81, 1, 6.1, 1.5) # trapezoidal channel with sideslope 3H:2V
+#' critical_depth(250, 2, 32.2, 100, 0) # rectangular channel
+#' critical_depth(126, 1, 9.81, 6.1, 1.5) # trapezoidal channel with sideslope 3H:2V
 #' @export
 critical_depth <- function(Q, yopt, g, B, SS) {
     .Call('rivr_critical_depth', PACKAGE = 'rivr', Q, yopt, g, B, SS)

R/graduallyvariedflow_v2.r

@@ -33,17 +33,17 @@ NULL
 #'   \item{Sf}{Friction slope.}
 #'   \item{E}{Total energy.}
 #'   \item{Fr}{Froude Number.}
-#' @details Computes the longitudinal water surface profile of a 
-#'   prismatic channel using the standard step method by solving the non-linear 
-#'   ODE \eqn{\frac{dy}{dx} = \frac{S_0 - S_f}{1 - Fr^2}}. The standard-step 
+#' @details Computes the longitudinal water surface profile of a prismatic 
+#'   channel using the standard step method by solving the non-linear ODE 
+#'   \eqn{\frac{dy}{dx} = \frac{S_0 - S_f}{1 - Fr^2}}. The standard-step 
 #'   method operates by stepping along the channel by a constant distance 
 #'   interval, starting from a cross-section where the flow depth is known 
 #'   (the control section). The flow depth is computed at the adjacent 
 #'   cross-section (target section). The computed value at the target is then 
 #'   used as the basis for computing flow depth at the next cross-section, i.e. 
 #'   the previous target section becomes the new control section for each step. 
 #'   A Newton-Raphson scheme is used each step to compute the flow depth and 
-#'   friction slope. Technically, the average friction slope of the control and 
+#'   friction slope. Technically, the average friction slope of the control and
 #'   target section is used to compute the flow depth at the target section.
 #' @examples
 #' \donttest{

man/compute_profile.Rd

@@ -47,9 +47,9 @@ data.frame with columns:
 Compute the gradually-varied flow profile of a prismatic channel.
 }
 \details{
-Computes the longitudinal water surface profile of a
-  prismatic channel using the standard step method by solving the non-linear
-  ODE \eqn{\frac{dy}{dx} = \frac{S_0 - S_f}{1 - Fr^2}}. The standard-step
+Computes the longitudinal water surface profile of a prismatic
+  channel using the standard step method by solving the non-linear ODE
+  \eqn{\frac{dy}{dx} = \frac{S_0 - S_f}{1 - Fr^2}}. The standard-step
   method operates by stepping along the channel by a constant distance
   interval, starting from a cross-section where the flow depth is known
   (the control section). The flow depth is computed at the adjacent

man/critical_depth.Rd

@@ -34,7 +34,7 @@ The critical depth is the water depth at which a channel
   \eqn{y = y_c} when \deqn{\frac{dE}{dy} = 1 - \frac{Q^2}{gA^3}\frac{dA}{dy} = 0}.
 }
 \examples{
-critical_depth(250, 32.2, 2, 100, 0) # rectangular channel
-critical_depth(126, 9.81, 1, 6.1, 1.5) # trapezoidal channel with sideslope 3H:2V
+critical_depth(250, 2, 32.2, 100, 0) # rectangular channel
+critical_depth(126, 1, 9.81, 6.1, 1.5) # trapezoidal channel with sideslope 3H:2V
 }
 

src/rivmech_characteristic_v7.cpp

@@ -127,7 +127,7 @@ double normal_depth(double So, double n, double Q, double yopt, double Cm,
     dy = ( pow(gp["A"], 5.0/3.0)/pow(gp["P"], 2.0/3.0) - n*Q/(Cm*sqrt(So)) ) / 
       ( gp["dAdy"]*(5.0/3.0)*pow(gp["A"]/gp["P"], 2.0/3.0) - 
       (2.0/3.0)*gp["dPdy"]*pow(gp["A"]/gp["P"], 5.0/3.0) );
-    yopt = yopt - dy;
+    yopt -= dy;
     i++;
   }
   return(yopt);  
@@ -150,8 +150,8 @@ double normal_depth(double So, double n, double Q, double yopt, double Cm,
 //' @param SS Channel sideslope [\eqn{L L^{-1}}].
 //' @return The critical depth \eqn{y_c} [\eqn{L}].
 //' @examples
-//' critical_depth(250, 32.2, 2, 100, 0) # rectangular channel
-//' critical_depth(126, 9.81, 1, 6.1, 1.5) # trapezoidal channel with sideslope 3H:2V
+//' critical_depth(250, 2, 32.2, 100, 0) # rectangular channel
+//' critical_depth(126, 1, 9.81, 6.1, 1.5) # trapezoidal channel with sideslope 3H:2V
 //' @export
 // [[Rcpp::export]]
 double critical_depth(double Q, double yopt, double g, double B, double SS){
@@ -162,9 +162,10 @@ double critical_depth(double Q, double yopt, double g, double B, double SS){
   int i = 0;
   while((fabs(dy) > tol) & (i < maxit)){
     NumericVector gp = channel_geom(yopt, B, SS);
-    dy = (pow(gp["A"], 3.0)/gp["dAdy"] - Q*Q/g) / 
-      (3*pow(gp["A"], 2.0) - pow(gp["A"], 3.0)*gp["dTdy"]/gp["dAdy"]);
-    yopt = yopt - dy;
+    dy = (pow(gp["A"], 3.0)/gp["dAdy"] - pow(Q, 2.0)/g) / 
+      (3.0*pow(gp["A"], 2.0) - pow(gp["A"], 3.0)*gp["dTdy"] / 
+      pow(gp["dAdy"], 2.0));
+    yopt -= dy;
     i++;
   }
   return(yopt);