From 4a65992df0a09af0bdab3879cc204a8d6e61d648 Mon Sep 17 00:00:00 2001
From: Antoine Cyril David Hoffmann <ahoffman@spcpc606.epfl.ch>
Date: Tue, 15 Dec 2020 17:35:52 +0100
Subject: [PATCH] to retrieve phase space distribution function

---
 matlab/compute_fa.m | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)
 create mode 100644 matlab/compute_fa.m

diff --git a/matlab/compute_fa.m b/matlab/compute_fa.m
new file mode 100644
index 00000000..750cfc20
--- /dev/null
+++ b/matlab/compute_fa.m
@@ -0,0 +1,23 @@
+function FF = compute_fa(Napj, spar, xperp)
+%% Compute the dispersion function from the moment hierarchi decomp.
+% Normalized Hermite
+Hp = @(p,s) polyval(HermitePoly(p),s)./sqrt(2.^p.*factorial(p));
+% Laguerre
+Lj = @(j,x) polyval(LaguerrePoly(j),x);
+% Maxwellian factor
+FaM = @(s,x) exp(-s.^2-x);
+
+[SS, XX] = meshgrid(spar, xperp); %meshgrid for efficient evaluation
+
+FF = 0 .* SS;
+
+[Pmax,Jmax] = size(Napj);
+
+FAM = FaM(SS,XX);
+for p_ = 0:Pmax-1
+    HH = Hp(p_,SS);
+    for j_ = 0:Jmax-1
+        LL = Lj(j_,XX);
+        FF = FF + Napj(p_+1,j_+1)*HH.*LL.*FAM;
+    end
+end
\ No newline at end of file
-- 
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