From 93241948bc82925ebdb0512d60808518a6bab475 Mon Sep 17 00:00:00 2001
From: Bartosz Kostrzewa <bartosz_kostrzewa@fastmail.com>
Date: Thu, 20 Feb 2020 21:03:07 +0100
Subject: [PATCH 1/2] add function for computing GL FSE correction factors

---
 R/gl_fse_corr.R | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)
 create mode 100644 R/gl_fse_corr.R

diff --git a/R/gl_fse_corr.R b/R/gl_fse_corr.R
new file mode 100644
index 000000000..f0902d0dc
--- /dev/null
+++ b/R/gl_fse_corr.R
@@ -0,0 +1,32 @@
+#' apply parameter-free Gasser-Leutwyler FSE corrections
+#' @details Apply FSE correction of a meson mass and decay constant
+#' based on eqs. 8 and 9 of Colangeo, Duerr, Haefeli [Nucl.Phys.B 721 (2005)]
+#' going back to Gasser and Leutwyler. Note that we employ the normalisation
+#' in which f_pi = 130.4.
+#' Note that \code{xi} and \code{lambda} below can be either of length one
+#' or of the same length as the vectors \code{Mps_V} and \code{fps_V}. When
+#' applying the correction to bootstrap samples, it might make sense
+#' to pass the original data values for \code{xi} and \code{lambda}.
+#' @param Mps_V Numeric vector, meson masses in any type of units. 
+#' @param fps_V Numeric vector, meson decay constants in the same units as
+#' \code{Mps_V}.
+#' @param xi Numeric vector, the ratio \eqn{M_{ps}^2 / (4 \pi f_\pi)^2}. Either of length
+#' one, in which case it is used for all \code{Mps_V} and \code{fps_V} or of the same
+#' length as \code{Mps_V} and \code{fps_V}. 
+#' @param lambda Numeric, the dimensionless product \eqn{M_{ps} \cdot L}. 
+#' @return Data frame with two columns containing the correction factors \code{K_mps}
+#' and \code{K_fps} for which we have:
+#' \deqn{ M_{ps}(L) = M_{ps}(\infty) \cdot K_{M_{ps} + \mathcal{O}(M_{ps} \xi^2) }
+#' \deqn{ f_{ps}(L) = f_{ps}(\infty) \cdot K_{f_{ps} + \mathcal{O}(f_{ps} \xi^2) }
+#' @export
+gl_fse_corr <- function(Mps_V, fps_V, xi, lambda){
+  stopifnot( length(xi) == length(lambda) )
+  stopifnot( length(Mps_V) == length(fps_V) )
+  if( length(xi) > 1 ){
+    stopifnot( length(xi) == length(Mps_V) )
+  }
+
+  g1_tilde <- g1(lambda)
+  return(data.frame(K_Mps = (1+0.5*xi*g1_tilde), K_fps = (1-2*xi*g1_tilde)))
+}
+

From 0444b7b209105c660b8cfc5821858bdca636cc0a Mon Sep 17 00:00:00 2001
From: Bartosz Kostrzewa <bartosz_kostrzewa@fastmail.com>
Date: Fri, 21 Feb 2020 12:09:20 +0100
Subject: [PATCH 2/2] remove outdated documentation and unnecessary parameters
 from gl_fse_corr

---
 R/gl_fse_corr.R | 18 ++----------------
 1 file changed, 2 insertions(+), 16 deletions(-)

diff --git a/R/gl_fse_corr.R b/R/gl_fse_corr.R
index f0902d0dc..18f2f3a33 100644
--- a/R/gl_fse_corr.R
+++ b/R/gl_fse_corr.R
@@ -3,29 +3,15 @@
 #' based on eqs. 8 and 9 of Colangeo, Duerr, Haefeli [Nucl.Phys.B 721 (2005)]
 #' going back to Gasser and Leutwyler. Note that we employ the normalisation
 #' in which f_pi = 130.4.
-#' Note that \code{xi} and \code{lambda} below can be either of length one
-#' or of the same length as the vectors \code{Mps_V} and \code{fps_V}. When
-#' applying the correction to bootstrap samples, it might make sense
-#' to pass the original data values for \code{xi} and \code{lambda}.
-#' @param Mps_V Numeric vector, meson masses in any type of units. 
-#' @param fps_V Numeric vector, meson decay constants in the same units as
-#' \code{Mps_V}.
-#' @param xi Numeric vector, the ratio \eqn{M_{ps}^2 / (4 \pi f_\pi)^2}. Either of length
-#' one, in which case it is used for all \code{Mps_V} and \code{fps_V} or of the same
-#' length as \code{Mps_V} and \code{fps_V}. 
+#' @param xi Numeric vector, the ratio \eqn{M_{ps}^2 / (4 \pi f_\pi)^2}. 
 #' @param lambda Numeric, the dimensionless product \eqn{M_{ps} \cdot L}. 
 #' @return Data frame with two columns containing the correction factors \code{K_mps}
 #' and \code{K_fps} for which we have:
 #' \deqn{ M_{ps}(L) = M_{ps}(\infty) \cdot K_{M_{ps} + \mathcal{O}(M_{ps} \xi^2) }
 #' \deqn{ f_{ps}(L) = f_{ps}(\infty) \cdot K_{f_{ps} + \mathcal{O}(f_{ps} \xi^2) }
 #' @export
-gl_fse_corr <- function(Mps_V, fps_V, xi, lambda){
+gl_fse_corr <- function(xi, lambda){
   stopifnot( length(xi) == length(lambda) )
-  stopifnot( length(Mps_V) == length(fps_V) )
-  if( length(xi) > 1 ){
-    stopifnot( length(xi) == length(Mps_V) )
-  }
-
   g1_tilde <- g1(lambda)
   return(data.frame(K_Mps = (1+0.5*xi*g1_tilde), K_fps = (1-2*xi*g1_tilde)))
 }