Matlab plot not showing correct values

Hi there,

Im trying to plot a graph using a for loop but the correct values are not being plotted. It is currently outputting the

same value 5 times. Any help would be appreciated.

clc;
clear;
hold on;
x=1:5;
grid on;

for i = 1:5
    v=0.1553567*(i.^6)-2.0416*(i.^5)+9.1837*(i.^4)-14.829*(i.^3)-1.3703*(i.^2)+32.821*(i)-1.3155

end

plot(x,v,".")

Answer 1

[Torsten]

v(i)=0.1553567*(i.^6)-2.0416*(i.^5)+9.1837*(i.^4)-14.829*(i.^3)-1.3703*(i.^2)+32.821*(i)-1.3155

instead of

v=0.1553567*(i.^6)-2.0416*(i.^5)+9.1837*(i.^4)-14.829*(i.^3)-1.3703*(i.^2)+32.821*(i)-1.3155

Answer 2

[dpb]

No need for and don't use loops here...

p=[0.1553567,-2.0416,9.1837,-14.829,-1.3703,32.821,-1.3155];    % store poly coefficients as vector
x=1:5;                                                          % x range desired
y=polyval(p,x);                                                 % calculate y(p(x)) at x
plot(x,y,'*')
grid on;

Your problem above is you're calculating on value at a time in the loop, but not saving in an array and not plotting until after the loop has finished. Hence, the value is always the last iteration through the loop; you've written over the previous loop value each time the loop executes.