FFT single sided spectrum imagesc plot

Hi guys

I have a matrix where I have performed an FFT operation, and I can view it using the imagesc function. However, I am seeing the negative spectrum as well, as shown in the figure below.

I have tried the using documentation of the single spectrum FFT from the web page but its not giving me what I want, as shown below:

%        Script 1 
% Try again removing negative spectrum
  
  L = length(tmp);
  P2 = abs(tmp/L);
  P1 = P2(1:L/2+1);
  P1(2:end-1) = 2*P1(2:end-1);
  figure
  imagesc(P1)

%        Script 2 
% here is another code snippet for removing the negative spectrum
 X_mags = abs(tmp);
 N_2 = ceil(L/2);
 figure
 imagesc(X_mags(1:N_2))

The output of the two separate scripts is shown below: definitely not what I want.

How can I only plot the positive spectrum of the matrix - with out using the fftshift?

Regards,