[讨论]大家来看看这段错哪了

[tqr591513792]

大家来看看这段错哪了
a=imread('f:\tu.jpg');
j=imnoise(a,'salt&pepper',0.02);
subplot(2,2,1),imshow(a)
subplot(2,2,2),imshow(j)
k=medfilt2(j);
subplot(2,2,3),imshow(k)
运行结果后出现??? Error using ==> imnoise
Unknown noise type: 'salt&pepper'.

Error in ==> e:\MATLAB6p5p1\work\zuoye.m
On line 2 ==> j=imnoise(a,'salt&pepper',0.02);