function res=safe_transition(xx,yy,x,y)global Map_Data VMAX% safe_transition: given a starting vector (xx,yy) and a target vector (x,y), this %                  function checks whether there are off-limits zones between%                  both places.% Arguments --------------------------------------------------------------%     (xx,yy) = coordinates of the starting place.%     (x,y) = coordinates of the target place.% Evaluation -------------------------------------------------------------%     test = boolean result of the check; 1 means 'safe transition'.%--------------------------------------------------------------------------% In verbose mode, there is no difference to silent mode.%--------------------------------------------------------------------------% MDP Toolbox, INRA, BIA Toulouse, France%--------------------------------------------------------------------------% Checking sizesif size(x,1)~=size(xx,1)    x=x';    y=y';end% Initialisationsres=zeros(size(x));res_temp=ones(size(x));% Masking the relevant X/=XX items from the vectortest=(x~=xx);x_t=test.*x+~test;y_t=test.*y+~test;xx_t=test.*xx+~test*2;yy_t=test.*yy+~test*2;% Computing the lines joining the pointsa=(y_t-yy_t)./(x_t-xx_t);b=y_t-a.*x_t;x_min=min(x_t,xx_t);x_m=abs(x_t-xx_t);% Checking every point from XX to X for safe transitionfor s=1:(3*VMAX),    absc=(x_min+(s/(3*VMAX))*x_m);    ord=round(a.*absc+b);    res_temp=res_temp & round(absc)>=1 & round(absc)<=size(Map_Data,2);    res_temp=res_temp & ord>=1 & ord<=size(Map_Data,2);    res_temp=res_temp & (Map_Data((round(absc)-1)*size(Map_Data,1)+ord)~=0);endres=res+test.*res_temp;res_temp=ones(size(x));% Masking the relevant X=XX, Y/=YY items from the vectortest=(y~=yy)&(x==xx);x_t=test.*x+~test;y_t=test.*y+~test;xx_t=test.*xx+~test*2;yy_t=test.*yy+~test*2;n_i=max(abs(y_t-yy_t));% Checking every point from XX to X for safe transitionfor s=1:n_i,   ord=round(min(yy_t,y_t)+(s/n_i)*(abs(y_t-yy_t)));   res_temp=res_temp & ord>=1 & ord<=size(Map_Data,2);   res_temp=res_temp & (Map_Data((x_t-1)*size(Map_Data,1)+ord)~=0);    end    res=res+test.*res_temp;res=res+((x==xx)&(y==yy));