Error in computing median filter and histogram equalization on an image. How can i solve it?

I am trying to perform median filter on an image using simple median filter code like this

a = imread('1a.jpg');
figure; imshow (a)
b = imnoise(a,'salt & pepper',0.02);
figure; imshow (b)
c = medfilt2(b);
figure; imshow (c)

but i am getting this error:

Error using medfilt2

Expected input number 1, A, to be two-dimensional.

Error in medfilt2>parse_inputs (line 107)

validateattributes(a, ...

Error in medfilt2 (line 48)

[a, mn, padopt] = parse_inputs(varargin{:});

Error in medianFilter (line 11)

c = medfilt2(b);

Also when i tried to perform histogram equalization also using this code

a = imread('1a.jpg');
img_eq = histeq(a); 
figure; imshow(img_eq);

I also get this error:

Error using histeq

Expected input number 1, I, to be two-dimensional.

Error in histeq (line 69)

validateattributes(a,{'uint8','uint16','double','int16','single'}, ...

Error in Histogramequalization (line 13)

img_eq = histeq(a);

How can i go about it pls.

Here are the two types of images i used.