help finding vector slope

hello all,

I am trying to plot a vector named vec1, where

 con = abs(g1-g2)/abs(t1:t2)*Fs));
 vec1 = [g1*ones(1,Fs*t1),con*ones(1,Fs*t2), g2*ones(1,Fs*t3)];

What I want to see is a graph that has a linear slope from t1 to t2.

There must be something wrong with the con variable, but I can't get my head around it. Any help?

Thank you in advance

[Azzi Abdelmalek]

what are g1,g2,...

Answer 1

[Youssef Khmou]

Try this :

 Fs=1000;
 T=(0:1/Fs:20-1/Fs);
 V=zeros(1,length(T));
 t1=3;
 t2=5;
 g1=7;
 g2=4;
 for t=1:length(T)

    if T(t)<=t1

        V(t)=g1;

    elseif T(t)>t1 && T(t) <=t2

        V(t)=-(g1-g2)/(t2-t1)*T(t)+1.65*g1;

    elseif T(t)>t2

        V(t)=g2;
    end
end
figure,
plot(T,V)
axis([0 20 0 10]), xlabel('time in Seconds');
ylabel(' Magnitude dB');title(' Gain')

[tony karamp]

Thank you for your response. I have a question though... How did you derive to that? (line 16)

vec(t)=-(g1-g2)/(t2-t1)*T(t)+1.65*g1;

where did you get the 1.65 from?

Thanks

[Youssef Khmou]

Tony, yes i forgot to mention that :

So your function in the 2dn region is defined as : y =ax+ b with negative slope :

vect(t) = a*T(t) + constant .

The slope is a= g1-g2/(t2-t1)= -3/2 .

to derive the constant : you take the initial condition :

At t=t1 vect(t1)=g1=a*t1+constant => constant=g1-a*t1=11.5 .

you can put 11.55 instead of g1*1.65 ,the reason i did g1*1.65 is because i derived the solution before you gave the details g1,t1,.. it was an approximation rather than solution from ax+b.

Answer 2

[tony karamp]

    |
    |
  g1|---------------\
    |                \
    |                 \
    |                  \ 
  g2|                   \---------------------
    |
    |_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
                   t1    t2                 t3

That's want I want to see!! Hope this helps!

Answer 3

[the cyclist]

You don't really give enough detail to diagnose this, but I did notice that in the line

con = abs(g1-g2)/abs(t1:t2)*Fs));

the parentheses are balanced, so it's not a valid MATLAB statement.

Answer 4

[Youssef Khmou]

hi, you have to declare all variables in your example like others said so as to examine the code , but now details are missing .

Answer 5

[tony karamp]

this is all I have

 Fs = 1000; %sampling frequency
 t1 = 3; %seconds
 t2 = 5;
 g1 = 7; %db
 g2 = 4

from 0 to t1, the gain is equal to g1. at t1, all the way to t2, there is a linear slope, decreasing for g1 to g2. from t2 to t3 the gain is equal to g2.

That is all I have...