The use of Sum()

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Joshua Adame 2019-8-19

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关闭： MATLAB Answer Bot 2021-8-20

I am not sure how to use the sum command can any one help me understand what I am doing wrong?

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Walter Roberson 2019-8-19

line() is only for drawing lines on the display.

You are passing in [x(1); x(9)] for the x component and [y(1); y(9)] for the y component, and you are doing that no matter what the value of i is. It is questionable what x(9) and y(9) are going to hold before you assign to x(i) and y(9) when i reaches 9. Effectively you are going to draw only two different lines: the same line for i = 1 to 8, and then a second different line when i reaches 9 so you overwrite x(9) and y(9), and the second line will be repeated for the remainder of the i iterations. It is not obvious why you are doing this.

Nishant Gupta 2019-8-22

Hi Joshua

First of all you cannot pass a line to the sum( ) function and can you send me the full code script so that I can help you further.

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Answer 1

Nishant Gupta 2019-8-23

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Hi Joshua

Like I previously mentioned in my comment, you cannot pass a line to the "sum( )" function. From the code it seems that you are trying to calculate the area under the given curve which is basically integration.

Refer to the following modified code script, it will help you :

x(1)= 0;
x(n)= 1;
h= 0.001;
n = (x(n) - x(1))/h;
area = 0;
sum1 = 0;
 
for i=1:n
       x(i + 1) = x(i) + h;
       y(i) = -9 * exp(-10 * x(i)) + 18 * exp(-15 * x(i))
       area = y(i) * h;
       sum1 = sum1 + area;
end