Use a for loop to evaluate

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Robert
Robert 2013-2-9
use a for loop to evaluate the function y = {exp(x+1) if x<-1, 2+cos(pi*x) if -1<=x<5, 10*(x-5)+1 if x>=5}
e^(x+1) if x<-1
y = {2+cos(pi*x) if -1<=x<5
10(x-5)+1 if x>=5
I am having trouble correctly setting up the for loop to store the values because the final product of this, is to plot the function y(x).
  2 个评论
Robert
Robert 2013-2-9
I forgot the range for the loop which is -2 to 6 increasing by 1 each time. Sorry!
Azzi Abdelmalek
Azzi Abdelmalek 2013-2-9
What have you done so far?

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回答（2 个）

Ahmed
Ahmed 2013-2-9
according to my little knowledge if you need to store this value for every loop in a Matrix where every inner for loop represent a row you can do this
if
y=zeros(9)
x=input('x=')
for i1=-2:6
y(i1)=.....
end
then y will be an array whose values are stored in the above Zero Matrix
Does this help ?
  1 个评论
Image Analyst
Image Analyst 2013-2-9
编辑：Image Analyst 2013-2-9
You cannot have zero or negative indexes, like -2 or -1 or 0. You can either add 3 to i1, or use a counter like I did in my Answer.

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Image Analyst
Image Analyst 2013-2-9
编辑：Image Analyst 2013-2-9
Try something like this:
index = 1;
for x = -2 : 1 : 6
if x < -1
% Insert code/formula here
y(index) = .........whatever.....
else if x >= -1 && x < 5
% Insert other code/formula here
else
% x >= 5
% Insert code/formula here
end
index = index + 1;
end
% Plot it.
plot(x,y, 'bo-', 'LineWidth', 3, 'MarkerSize', 15);
title('Plot of y vs. x', 'FontSize', 25);
  2 个评论
Robert
Robert 2013-2-10
Thank you. I will ask if you could generically go where the y(index) first appears. Basically what would the "whatever" be? I'm still very new to Matlab
Image Analyst
Image Analyst 2013-2-10
You insert the appropriate formula from your question:
y = e^(x+1) if x<-1
y = {2+cos(pi*x) if -1<=x<5
y = 10(x-5)+1 if x>=5

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