Match map plot direction to a vector3d

vector3dnwse.m

@@ -0,0 +1,98 @@
+function vecOut = vector3dnwse(nwseIn)
+% find the vector3d corresponding to a NWSE map plot direction
+% so you can do something like vector3d.x but instead vector3d.north
+% nwseIn should be a character array or number
+
+
+%% 1. find out where in the map (NWSE) points along X,-X,Y,-Y
+%up to one of these is empty
+dirX = getMTEXpref('xAxisDirection');
+dirY = getMTEXpref('yAxisDirection');
+dirZ = getMTEXpref('zAxisDirection');
+
+% UpDown outputs {1 2} {'outOfPlane','intoPlane'};
+% NWSE outputs {1 2 3 4} from {'east','north','west','south'}
+
+if ~isempty(dirZ)
+    vZ = UpDown(dirZ);
+else
+    try
+        % if Z points out, mod(vX,4) is smaller than mod(vY,4)
+        vX = NWSE(dirX);
+        vY = NWSE(dirY);
+        if mod(vX,4) < mod(vY,4)
+            vZ = 1;
+        elseif mod(vX,4) > mod(vY,4) %otherwise Z must point in
+            vZ = 2;
+        end
+    catch
+        %either the coordinates are badly defined or something went wrong
+        error('vector3dnwse: which way is Z pointing?');
+    end
+end
+
+if ~isempty(dirX)
+    vX = NWSE(dirX);
+else
+    try
+        vY = NWSE(dirY);
+        if vZ == 1  % Z points out, so X < Y
+            vX = checkmod(mod(vY-1,4));
+        elseif vZ == 2 %otherwise Z points in so X > Y
+            vX = checkmod(mod(vY+1,4));
+        end
+        if vX==0 %mod(0,4) and mod(4,4) both to zero but we don't want this
+            vX=4;
+        end
+    catch
+        %either the coordinates are badly defined or something went wrong
+        error('vector3dnwse: which way is X pointing?');
+    end
+end
+
+if ~isempty(dirY)
+    vY = NWSE(dirY);
+else
+    try
+        if vZ == 1 % Z points out, so X < Y
+            vY = checkmod(mod(vX+1,4));
+        elseif vZ == 2 %otherwise Z points in so X > Y
+            vY = checkmod(mod(vX-1,4));
+        end
+    catch
+        %either the coordinates are badly defined or something went wrong
+        error('vector3dnwse: which way is Y pointing?');
+    end
+end
+
+vXminus = checkmod(mod(vX+2,4));
+vYminus = checkmod(mod(vY+2,4));
+
+%% 2. output a vector3d(+-XY) according to the input map direction (NWSE)
+vList = [vX; vXminus; vY; vYminus];
+vPos = find(vList==NWSE(nwseIn));
+
+switch vPos
+    case 1
+        vecOut = vector3d.X;
+    case 2
+        vecOut = -vector3d.X;
+    case 3
+        vecOut = vector3d.Y;
+    case 4
+        vecOut = -vector3d.Y;
+end
+
+
+    function [vOut] = checkmod(vIn)
+    %mod(0,4) and mod(4,4) both output zero but we actually want 4
+        if vIn==0
+            vOut=4;
+        else
+            vOut=vIn;
+        end
+    end
+
+end
+
+