Question

matlab

Answer 1

You forgot to add -1^n for your Taylor series of sin(x).

Answer 2

@yagosik thanks

Answer 3

@raffle_snaffle No problem.

Answer 4

Sorry, but what do you need to get as a result?

Answer 5

@ikram002p

Answer 6

My code isn't running in the order I want it to run. The assignment is attached.

Answer 7

I just can't get the prompts correct. I want it to ask the user...

Which func would you like to use? say i choose 1

The func chosen is: 1

next... Input an x value: says we enter 2

then it ends.

I need the code to run properly if I chose either func 1 or 2.

Answer 8

@phi

Answer 9

First, I don't understand your use of the variable "func"

Answer 10

clear, clc % clears command and workspace window

% define variables
max_iters = 1:150;
n = 0;
allowed_error = 0.005;
% function_1 is eulers
% function_2 is sin
% asking user which function to operate
func = input('Which function would you like to use, 1 or 2: ');
if (func == 1)
fprintf('You chose function 1. ');
end
% asking user to input a x value
x = input('Input an x value: ');
if ((x >= -50) && (x <= 50))
elseif error ('x must be x >= -50 and x <=50 ')
end

% while loop for eulers
while (n <= max_iters)
func = (x^(n))/(factorial(n));
n = n + 1;

if (func <= allowed_error)
break
end
end

if (func == 2)
fprintf('You chose function 2. ');
end
% asking user to input a x value
x = input('Input an x value: ');
if ((x >= -50) && (x <= 50))
elseif error ('x must be x >= -50 and x <= 50')
end

% while loop for sin
while (n <= max_iters)
func = ((-1)^n)*(x^(2*n+1))/(factorial(2*n+1));
n = n + 1;
fprintf('continue iterations');
if (func <= allowed_error)
break
end
end

Answer 11

I am sorry @phi I misunderstood your question

Answer 12

func is either eulers or sin

Answer 13

The assignment is very specific about what they want, and your code is not very close to what they want.

Answer 14

It is easier to debug if it's not a function (though you could use the debugger)

but they are expecting you to write a function with 4 parameters, and it returns a 0 or 1, and the number of iterations it takes to converge (if it did)

Answer 15

the input parameter func is supposed to be a string, e.g. 'sin' or 'exp'

they want you to use a "switch" statement, not if/then

Answer 16

okay

Answer 17

meanwhile,

***
if ((x >= -50) && (x <= 50))
elseif error ('x must be x >= -50 and x <= 50')
end
***

the syntax/logic should be
if ( (x< -50) || (x>50) ) error ('x must be x >= -50 and x <= 50'); end;

Answer 18

your statement:

***
if ((x >= -50) && (x <= 50))
elseif error ('x must be x >= -50 and x <= 50')
end
***

the elseif error part is not strictly correct.
slightly better would be
if ((x >= -50) && (x <= 50))
else error ('x must be x >= -50 and x <= 50')
end

but that is a bit muddled.

the most straight forward way to do the test is to "throw an error" if x is out of bounds:
if ( (x< -50) || (x>50) ) error ('x must be x >= -50 and x <= 50'); end;

Answer 19

"or" instead of an "and", okay.

Answer 20

we can fix up your code, but it is not what the assignment asks for.

Answer 21

Do I need to use switch, instead of if else statements? I am not familiar with "switch"

Answer 22

So both functions, eulers and sin are going to be in the same m file or have their own m file?

Answer 23

rather than ask the user for input, I would "hard-wire" the input... because after you get the script to execute properly, you will change it into a function.

Answer 24

if you are going to create a function, but use a script for debugging, I would start with

%function [converges, iter] = ...
% taylor series(func, x, allowed_error , max_iters)

and then copy the comments given in the problem.

next, I would define values for the params (these are test values)

% REMOVE in the real function
func= 'sin';
x= 0.5;
allowed_error= 1e-5;
max_iters= 100;
% REMOVE in the real function

Answer 25

Let me think

Answer 26

the first thing we do is check the input variables. Something like this:
% check that input values are within bounds
if ( (x<-50) || (x>50) ) error('x must be between -50 and +50'); end;
if (allowed_error< 1e-12) error('allowed error must be >= 1e-12'); end;
if ( (max_iters<1) || (max_iters>150))
error('max number of iterations must be from 1 to 150');
end;
% check that func is a valid string
validStrings = {'sin','exp'};
validStr = validatestring(func,validStrings)

Answer 27

next, for each func choice, evaluate the taylor series terms.
We don't care about the sign (we want positive terms), so we can ignore (-1) part in the sine


% taylor series terms
converges= 0; iter= 0;
switch func
case 'sin'
% taylor series
for n=0:(max_iters-1)
kk= 2*n+1;
tt= x^kk/factorial(kk);
if (tt<allowed_error)
converges= 1;
iter= n+1;
break;
end; %if we converged
end; % for

case 'exp'
for n=0:(max_iters-1)
tt= x^n/factorial(n);
if (tt<allowed_error)
converges= 1;
iter= n+1;
break;
end; %if we converged
end; % for

otherwise
error('invalid function name');

end; % switch

% REMOVE in the real function
fprintf('%s converges %d iter %d\n', func, converges, iter);
% REMOVE in the real function

Answer 28

% define variables
n = 0;

% function 1 is eulers
% function 2 is sin
iter = 0;
converges = 0;

% if else statement for eulers
if (func == 'exp')
% while loop for eulers
func = (x^(n))/(factorial(n));
n = n + 1;
if (func <= allowed_error)
converges = 1;
iter = n;
break
end
end

else
fprintf('You chose function 2. \n');

% while loop for sin
while (n <= max_iters)
func = ((-1)^n)*(x^(2*n+1))/(factorial*(2*n+1));
n = n + 1;
if (abs(func) <= allowed_error)
convergs = 1;
iter = n;
break
end
end
end

Answer 29

I think the assignment calls for while loops not for loops.