Display data in a while loop as a table

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rezheen
rezheen 2025-5-16
编辑： Torsten 2025-5-16
Hello, I'm trying to approximate the root of a function using Newton's method and display the results as a table. I've found my results but am having trouble displaying the table appropriately. I have a function file, and a script. This is my code:
Function:
function x = newtonimproved_4_7(f,df,x0,tol)
x=x0; y=f(x); n=0;
while abs(y)>tol
n=n+1;
x=x-y/df(x);
y=f(x);
t=table(n',x',y');
header={'n','x_n','f(x_n)'};
t.Properties.VariableNames=header;
disp(t)
end
Script:
clear, clc
format longg
f=@(x) x^3-5; df=@(x) 3*x^2;
newtonimproved_4_7(f,df,1,0.00001);
Also, if I can decompose all of it into just a script file and perhaps use syms instead, that'd be great, but that's not the main premise of this question.
Thanks.
  1 个评论
ScottB
ScottB 2025-5-16
I don't have MATLAB in front of me at the moment but it seems that you should define a table before the loop and add entries to it in the loop then display the table after the loop has completed and you have reached the defined tolerance.
I think the current code is repeatedly defining a table with one set of entries, displaying that table then overwriting it in the next interation of the loop.

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采纳的回答

Steven Lord
Steven Lord 2025-5-16
Ran in:
Rather than building a new table each time, I'd create one before your loop and add to it then display it at the end.
f=@(x) x^3-5; df=@(x) 3*x^2;
newtonimproved_4_7(f,df,1,0.00001);
n x_n f(x_n) _ ______ __________ 1 2.3333 7.7037 2 1.8617 1.4523 3 1.722 0.10624 4 1.7101 0.00073505 5 1.71 3.6014e-08
function x = newtonimproved_4_7(f,df,x0,tol)
x=x0; y=f(x); n=0;
header={'n','x_n','f(x_n)'};
t = table('Size', [0 3], ...
'VariableTypes', ["double", "double", "double"], ...
'VariableNames', header);
while abs(y)>tol
n=n+1;
x=x-y/df(x);
y=f(x);
t(end+1, :) = {n, x, y};
end
disp(t)
end

更多回答（1 个）

Torsten
Torsten 2025-5-16
编辑：Torsten 2025-5-16
Ran in:
clear, clc
format longg
f=@(x) x^3-5; df=@(x) 3*x^2;
[n,X,Y] = newtonimproved_4_7(f,df,1,0.00001);
t=table((1:n).',X',Y');
header={'n','x_n','f(x_n)'};
t.Properties.VariableNames=header;
disp(t)
n x_n f(x_n) _ ________________ ____________________ 1 2.33333333333333 7.7037037037037 2 1.86167800453515 1.45228738979579 3 1.72200188005861 0.106235772741379 4 1.71005973660029 0.000735045685184232 5 1.70997595078219 3.601359477301e-08
function [n,X,Y] = newtonimproved_4_7(f,df,x0,tol)
x=x0; y=f(x); n=0;
X(1) = x; Y(1) = y;
while abs(y)>tol
n=n+1;
x=x-y/df(x);
y=f(x);
X(n) = x;
Y(n) = y;
end
end

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