i need help with this?

Consider the function defined by g(x) =sin(πx), x ∈ (−1, 1] x^4 − 1, x ∈ [−1.5, −1] ∪ (1, 1.5] (a) Write a MATLAB function gxsin that takes as input a vector x, and returns a vector y that contains the corresponding values of the function g. (b) Using the function gxsin and a suitable array x containing 102 entries, write appropriate MATLAB commands that produce a plot of the function defoned above. The plot should be entitled "Plot of g(x) vs x". THIS IS WHAT I HAVE:

function y = gxsin(x)

for i=1:length(x)

 if (x(i)> -1) && (x(i)<=1)
g(i)=sin(pi*x(i));
elseif (x(i)>=-1.5) && (x(i)<=-1)|| (x(i)>1) && (x(i)<=1.5)
g(i)= ((x.^4 -1));
    end
end
end
x=linspace(-1.5,1.5,102);
y=gsxin(x), I'm getting an error when i type this part

[Torsten]

You see the error in the line

g(i)= ((x.^4 -1));

?

Answer 1

[madhan ravi]

Make a note a loop is not needed to do this operation , logical indexing is better and efficient, you got error becuaw you didn't define gsxin(x) function like I did

LOGICAL INDEXING WAY

x=linspace(-1.5,1.5,102);
y=gsxin(x); %function calling
plot(x,y)

function g=gsxin(x)   %function definition
id=(x> -1) & (x<=1);
g(id)=sin(pi*x(id));
id1=((x>=-1.5) & (x<=-1))| ((x>1) & (x<=1.5));
g(id1)= (x(id1).^4 -1);
end

LOOP WAY

x=linspace(-1.5,1.5,102);
y=gsxin(x); %function call
plot(x,y)

function g=gsxin(x)  %function definition 
g=zeros(1,numel(x)); %pre-allocation
for i =1:numel(x)
if (x(i)> -1) && (x(i)<=1)
g(i)=sin(pi*x(i));
elseif (x(i)>=-1.5) && (x(i)<=-1)|| (x(i)>1) && (x(i)<=1.5)
g(i)= (x(i).^4 -1);
    end
end
end

[Tawanda Le Bourne]

thank you, i found my error

madhan ravi's reply : Anytime :)

[Tawanda Le Bourne]

Can you help me with this one please.

Consider the sequence defined by xn+1 = xn − tan(xn) for some initial value x0. (a) Write a MATLAB function seqtan that takes the values x0 and etol as inputs, and calculates the terms of the sequence above until the stopping criterion xn+1 − xn/|xn+1|< etol is satisfied. The function should output the final calculated term of the sequence and store the value as x.

(b) Write a MATLAB command that executes seqtan with x0 = 8 and etol = 2 × 10^−10 and stores the resulting output as u.

I DON'T UNDERSTAND THIS ONE

madhan ravi's reply : post a separate question by providing all the necessary details

[Tawanda Le Bourne]

THIS IS WHAT I DID function x= seqtan(x0,etol)

x=1;

y=x-tan(x);

x=y;

while delta > etol

    y=x-tan(x);

    delta=abs(y-x)

    x=y;
end