FFT in for Loop

This code is not wroking I want to create a for loop to perform FFT

M = 1:100
dt =.1
time = 0:0.5:(length(M)-1)/2
samplerate=1/dt;
J= length(S)/samplerate-dt
t = 0:1/samplerate:(J)    %0:1/200:length(time)-1; 
L = length(t)
f = samplerate*(0:(L/2))/L;
 dat1 = f(1,:).';
for i = 1:10
MM(:,i) = FLOW(:,i)
y(:,i)  = fft(MM(:,i))%fft(FLOW(:,i))
P20 = abs(y(:,i)/L)
P10(:,i)= P20((:,i)(1:L/2+1)))
P10(2:end-1) = 2*P10(2:end-1)
  A = ( P10(:,i)); 
    dat1 =[dat1,A];
end

[KSSV]

This code is not wroking

Why? what is the error/ problem?

[Joshua David Selvaraj]

P10= P20(1:L/2+1)

using this makes the code work but the problem is i need to keep the counter (i) to get continued so that I can save them in dat1

[Siriniharika Katukam]

What is "S" in line 5 and "FLOW" in first line of for loop?

[JoshuaDavid Selvaraj]

P10= P20(1:L/2+1,:) this works i fixied it however thans for your support