function b=femval_stat(x,y,expr,femstr)
%FEMVAL_STAT
%   B = FEMVAL_STAT(X,Y,EXPR,FEMSTR) returns the values B of
%   the expression EXPR for the FEM-structure with the name FEMSTR
%   at points specified by X and Y. The FEM-structure with the name
%   FEMSTR must be present in the main MATLAB work space and have
%   a solution, that is, a field sol.u.
%
%   Note that the mesh for the current model using FEMVAL_STAT does not
%   need to be the same as the mesh in the FEM-structure with the name
%   FEMSTR. Values of B for coordinates that are outside the mesh
%   will be NaN.
%
%   Example:
%   Given a FEM-structure fem1 in the main MATLAB work space with a solution
%   and defining the variable ux on subdomain level. Another model
%   in the GUI is loaded, possibly with a different mesh. In this model,
%   a PDE coefficient, boundary coefficient, or initial value can be set
%   to 'femval_stat(x,y,'ux','fem1')'. An expression including femval_stat
%   can also be used directly in the expressions in the post mode dialog boxes.
%
%   Cautionary:
%   FEMVAL_STAT and FEMVAL_TIME take x and y as input and uses postinterp
%   on these points. This means that for coordinates being mesh nodes
%   between elements with a discontinuity between them, postinterp will
%   just "choose" the value from one of the elements. This can be a
%   problem when trying to plot discontinuities using these functions in,
%   e.g., POSTPLOT, or entering them in the Plot Parameters dialog box.
%   However, when integrating with POSTINT, or using the Integration dialog
%   boxes, evaluation is only done in internal points, so no such coordinates
%   will be passed to FEMVAL_STAT and FEMVAL_TIME, hence this is not a problem.
%
%   See also FEMVAL_TIME.

oldfem=evalin('base',femstr);
b=postinterp(oldfem,expr,[x(:)';y(:)']);
b=reshape(b,size(x));