help needed on Bandwidth over certain thredshold in a loop

I am new to Matlab and hope someone can help me out. I try to get the bandwidth at certain reading of a peak, and write the following code. But run into a few problems. The codes are follows.

%%%read in data%%%%

origindata=importdata('rawdata.txt');

f=origindata(:,1);

a=origindata(:,2);

b=origindata(:,3);

c=origindata(:,4);

d=origindata(:,5);

%%% loop t for calculation %%%

y=0;

for t=(0.1:0.1:20)

e=a-j*b;

u=c-j*d;

rl=(u./e).*f*t;

%%%%save results%%%

y=y+1;

y1(:,3*y-2)=f;

y1(:,3*y-1)=rl;

y1(:,3*y)=t;

%%%find minimum and bandwidth%%%%

RLmax=min(rl);

w1=f(f(abs(rl+10)<0.1)<f(rl==RLmax));

w2=f(f(abs(rl+10)<0.1)>f(rl==RLmax));

width=w2-w1;

%%%%save results at each t%%%

z1(y,1)=t;

z1(y,2)=f(rl==RLmax);

z1(y,3)=RLmax;

z1(y,4)=w1;

z1(y,5)=w2;

z1(y,6)=width;

thickness=z1(:,1);

frequency=z1(:,2);

peak=z1(:,3);

frequency1=z1(:,4);

frequency2=z1(:,5);

bandwidth=z1(:,6);

hold on;

end;

%%%%find minimum and bandwidth over all the t and save final results%%%%

p = min(z1(:,3));

th = thickness(z1(:,3)==p);

freq = frequency(z1(:,3)==p);

freq1 = frequency1(z1(:,3)==p);

freq2 = frequency2(z1(:,3)==p);

bandwid = bandwidth(z1(:,3)==p);

z1(y+3,1)=th;

z1(y+3,2)=freq;

z1(y+3,3)=p;

z1(y+3,4)=freq1;

z1(y+3,5)=freq2;

z1(y+3,6)=bandwid;

%%%%save results in files%%%

xlswrite('y1',y1);

xlswrite('z1',z1);

Error message after run:

"Unable to perform assignment because the size of the left side is 1-by-1 and the size of the

right side is 0-by-1."

It seemed the following codes caused problem, as I removed them and related, it ran ok.

w1=f(f(abs(rl+10)<0.1)<f(rl==RLmax));

w2=f(f(abs(rl+10)<0.1)>f(rl==RLmax));

width=w2-w1;

But I need to extract those to extract bandwidth information. Can anyone help me out? Thank you.