how do i make one function that i am able to use trapezoidal rule for integration from this code?

x=0:0.01:25; 
y=zeros;
for T1=1:length(x)
    if x(T1)>=0 && x(T1)<5
         y(T1)=0.1553567*(x(T1)^6)-2.0416*(x(T1)^5)+9.1837*(x(T1)^4)-14.829*(x(T1)^3)-1.3703*(x(T1)^2)+32.821*(x(T1))-1.3155;
         hold on
    elseif x(T1)>=5 && x(T1)<15.4
        y(T1)=0.003980879*(x(T1)^5)-0.2247*(x(T1)^4)+4.8682*(x(T1)^3)-50.442*(x(T1)^2)+254.67*(x(T1))-430.66;\r\n
        hold on    
    else ;x(T1)>=15.4;
        y(T1)=-0.073*(x(T1)^2)+6.1802*(x(T1))+40.423;
    end
end

[Star Strider]

Please do not close Questions that have Answers.

[John D'Errico]

When you edit away your question, you insult the person who made the effort to answer your question.

[John D'Errico]

Stop closing the question. We will just keep reopening it. If you felt it was important enough to ask, then someone else might learn something from it too. If you are worried that your teacher will read what you asked, then you should never have asked the question in a public forum.

[Rena Berman]

(Answers Dev) Restored edit

[Rena Berman]

(Answers Dev) Restored edit

Answer 1

[Star Strider]

One option:

yx = @(x) (0.1553567*(x.^6)-2.0416*(x.^5)+9.1837*(x.^4)-14.829*(x.^3)-1.3703*(x.^2)+32.821*(x)-1.3155).*((x>=0) & (x<5)) + (0.003980879*(x.^5)-0.2247*(x.^4)+4.8682*(x.^3)-50.442*(x.^2)+254.67*(x)-430.66).*((x>=5) & (x<15.4)) + (-0.073*(x.^2)+6.1802*(x)+40.423).*(x>=15.4);
x=0 : 0.01 : 25;
y_int1 = trapz(x, yx(x))                        % Use ‘trapz’
y_int2 = integral(yx, 0, 25)                    % Use ‘integral’

y_int1 =
          2457.58206158505

y_int2 =
          2457.58239477744