MATLAB: Write a script that calculates the user produced polynomial. The polynomial can be input until the user decides to terminate the program.

homeworklooppolynomial

Hello,

I've been given an asignment in school and I'm a bit stuck with this task in the title.

Can anyone help me write the script because I don't know how to create a polynomial that is user decided and loop it at the same time?

Thanks in adwance.

Best Answer

If you have the Symbolic Math Toolbox and wish to manipulate the polynomials in symbolic form, you can use poly2sym,

>> p = input('\nEnter polynomial coefficients: ')
Enter polynomial coefficients: [1,1,0,-1]
p =
     1     1     0    -1
>> P=poly2sym(p)
 
P =
 
x^3 + x^2 - 1

However, that's often unnecessary. There are many Matlab commands that can analyze polynomials given only a vector representing their coefficients, e.g.,

>> roots(p)  %roots of the polynomial
ans =
  -0.8774 + 0.7449i
  -0.8774 - 0.7449i
   0.7549 + 0.0000i

Related Solutions

MATLAB: Model for fitting polynomial of degree 3

Just read the help.

x = rand(10,1);
>> y = rand(10,1);
>> D = dataset(x,y);
>> fitlm(D,'poly3')
ans = 
Linear regression model:
    y ~ 1 + x + x^2 + x^3
Estimated Coefficients:
                        Estimate                SE                  tStat                 pValue      
                   __________________    _________________    __________________    __________________
    (Intercept)     0.883325330921357    0.269610952016709      3.27629617533717    0.0169006334507573
    x              -0.905689721171103     2.50947007046528     -0.36090875592837      0.73053441711432
    x^2              2.97715513265619     5.78699413259576     0.514456221043511     0.625326610386953
    x^3             -2.49404374290891     3.78096082734174    -0.659632261956649      0.53397526842927
Number of observations: 10, Error degrees of freedom: 6
Root Mean Squared Error: 0.182
R-squared: 0.222,  Adjusted R-Squared: -0.167
F-statistic vs. constant model: 0.57, p-value = 0.655

I could also have written the model as:

fitlm(D,'y ~ 1 + x + x^2 + x^3')

which produces the same result.

MATLAB: How to plot a linear function in using for loop in matlab

You need to add ‘no_of_points’ as an argument to your ‘findCoodinates’ function. You also need to subscript ‘y’ in it, to return a vector rather than a single value.

slope = input('\nEnter the slope:');
y_intercept = input('\nEnter the y_intercept:');
no_of_points = input('\nEnter no_of_points:');
[x,y] = findCoodinates(slope,y_intercept,no_of_points);
plot(x,y, 'ko-');
xlabel('x-axis');
ylabel('y-axis');
legend('First Graph');
axis([0 20 -5 30])
% here is the (function)
function [x,y] = findCoodinates(m,b,no_of_points)
for i = 1:no_of_points
    x(i) = i;
    y(i) = x(i)*m + b;
end
end

With those changes, your code worked when I ran it.

Best Answer

Related Solutions

MATLAB: Model for fitting polynomial of degree 3

MATLAB: How to plot a linear function in using for loop in matlab

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