type BiSmooth.m % smooth image A using a binomial filters of order p (should be even) function [SI] = BiSmooth(A,p); X = [1 2 1]; c = 4; for i=2:2:p-2, X = conv(X,[1 2 1]); c = c*4; end; I1 = filter2(X/c,A); I2 = filter2(X'/c,I1); SI = uint8(I2); conv([1 2 1],[1 2 1]) ans = 1 4 6 4 1 X = conv([1 2 1],[1 2 1]) X = 1 4 6 4 1 conv(X,X) ans = 1 8 28 56 70 56 28 8 1 conv(X,[ 1 2 1]) ans = 1 6 15 20 15 6 1 SI1 = BiSmooth(Ig, 2); SI4 = BiSmooth(Ig, 4); SI3 = BiSmooth(Ig, 16); figure, imshow(SI1); Warning: Image is too big to fit on screen; displaying at 75% scale. > In truesize>Resize1 at 308 In truesize at 44 In imshow at 161 Warning: line XData length (4) and YData length (2) must be equal. > In graphics.zoom.buttonmotionfcn2D at 66 In graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 Warning: line XData length (2) and YData length (4) must be equal. Warning: line XData length (4) and YData length (2) must be equal. Warning: line XData length (4) and YData length (2) must be equal. Warning: line XData length (2) and YData length (4) must be equal. Warning: line XData length (4) and YData length (2) must be equal. > In graphics.zoom.buttonmotionfcn2D at 66 In graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. figure(1); imshow(Ig) Warning: Image is too big to fit on screen; displaying at 75% scale. > In truesize>Resize1 at 308 In truesize at 44 In imshow at 161 ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. figure, imshow(SI2); ??? Undefined function or variable 'SI2'. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. figure, imshow(SI4); Warning: Image is too big to fit on screen; displaying at 75% scale. > In truesize>Resize1 at 308 In truesize at 44 In imshow at 161 figure, imshow(SI3); Warning: Image is too big to fit on screen; displaying at 75% scale. > In truesize>Resize1 at 308 In truesize at 44 In imshow at 161 ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. SI2 = SI4; whos Name Size Bytes Class I 480x640x3 921600 uint8 array Ig 480x640 307200 uint8 array SI1 480x640 307200 uint8 array SI2 480x640 307200 uint8 array SI3 480x640 307200 uint8 array SI4 480x640 307200 uint8 array X 1x5 40 double array ans 1x7 56 double array Grand total is 2457612 elements using 2457696 bytes clear SI4 whos Name Size Bytes Class I 480x640x3 921600 uint8 array Ig 480x640 307200 uint8 array SI1 480x640 307200 uint8 array SI2 480x640 307200 uint8 array SI3 480x640 307200 uint8 array X 1x5 40 double array ans 1x7 56 double array Grand total is 2150412 elements using 2150496 bytes type BiSmooth.m % smooth image A using a binomial filters of order p (should be even) function [SI] = BiSmooth(A,p); X = [1 2 1]; c = 4; for i=2:2:p-2, X = conv(X,[1 2 1]); c = c*4; end; I1 = filter2(X/c,A); I2 = filter2(X'/c,I1); SI = uint8(I2); type Gradient.m % Partial derivatives in X and Y directions function [Gx,Gy] = Gradient(A, p); X = [-1 0 1]/2; % filter Y = [1 0 -1]'/2; % filter Gx = filter2(X,A); % correlation Gy = filter2(Y,A); [M,N] = size(A); Gx(1:p+1,:) = 0; Gx(M-p-1:M,:) = 0; Gx(:,1:p+1) = 0; Gx(:,N-p-1:N) = 0; Gy(1:p+1,:) = 0; Gy(M-p-1:M,:) = 0; Gy(:,1:p+1) = 0; Gy(:,N-p-1:N) = 0; [Gx, Gy] = Gradient(Ig, 1); help quiver QUIVER Quiver plot. QUIVER(X,Y,U,V) plots velocity vectors as arrows with components (u,v) at the points (x,y). The matrices X,Y,U,V must all be the same size and contain corresponding position and velocity components (X and Y can also be vectors to specify a uniform grid). QUIVER automatically scales the arrows to fit within the grid. QUIVER(U,V) plots velocity vectors at equally spaced points in the x-y plane. QUIVER(U,V,S) or QUIVER(X,Y,U,V,S) automatically scales the arrows to fit within the grid and then stretches them by S. Use S=0 to plot the arrows without the automatic scaling. QUIVER(...,LINESPEC) uses the plot linestyle specified for the velocity vectors. Any marker in LINESPEC is drawn at the base instead of an arrow on the tip. Use a marker of '.' to specify no marker at all. See PLOT for other possibilities. QUIVER(...,'filled') fills any markers specified. QUIVER(AX,...) plots into AX instead of GCA. H = QUIVER(...) returns a quivergroup handle. Backwards compatibility QUIVER('v6',...) creates line objects instead of a quivergroup object for compatibility with MATLAB 6.5 and earlier. Example: [x,y] = meshgrid(-2:.2:2,-1:.15:1); z = x .* exp(-x.^2 - y.^2); [px,py] = gradient(z,.2,.15); contour(x,y,z), hold on quiver(x,y,px,py), hold off, axis image See also feather, quiver3, plot. Reference page in Help browser doc quiver Ind = find(Gx.^2 + Gy.^2 > 25); [IndX, IndY] = find(Gx.^2 + Gy.^2 > 25); quiver(IndX, IndY, Gx(Ind), Gy(Ind)); figure, quiver(IndX, IndY, Gx(Ind), Gy(Ind)); ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. figure, quiver(-IndY, IndX, -Gy(Ind), Gx(Ind)); ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. ??? Invalid handle object. Error in ==> graphics.zoom.buttondownfcn2D>local2DButtonMotionFcn at 94 buttonmotionfcn2D(hZoom); ??? Error while evaluating figure WindowButtonMotionFcn. figure, quiver(IndY, -IndX, Gy(Ind), -Gx(Ind)); figure, quiver(IndY, -IndX, Gx(Ind), -Gy(Ind)); figure, quiver(IndY, -IndX, Gx(Ind), Gy(Ind)); [Gx3, Gy3] = Gradient(SI3, 1); Ind3 = find(Gx3.^2 + Gy3.^2 > 25); [IndX3, IndY3] = find(Gx3.^2 + Gy3.^2 > 25); figure, quiver(IndY3, -IndX3, Gx3(Ind3), Gy3(Ind3)); diary