forums.silverfrost.com

pban92 · Joined: 23 Nov 2009 Posts: 38

Hello,

Here is my original function

and I am trying to code to generate data to create this mirrored and shifted function as in this figure

To further clarify, my array which contains,
x y
1 10.8
2 10.0
3 9.1
4 8.0
5 6.8
6 6.0
7 5.2
8 4.3
9 3.0
10 0.0

and I am trying to make a new array like,

x y
1 0.0
2 3.0
3 4.3
4 5.2
5 6.0
6 6.8
7 8.0
8 9.1
9 10.0
10 10.8
11 10.8
12 10.0
13 9.1
14 8.0
15 6.8
16 6.0
17 5.2
18 4.3
19 3.0
20 0.0

Here is my code which is giving error,

Wilfried Linder · Posted: Thu Mar 10, 2011 6:33 pm Post subject:

May be, the last part of your code should be like this:

pban92 · Joined: 23 Nov 2009 Posts: 38

This solved the problem.

JohnCampbell · Joined: 16 Feb 2006 Posts: 2615 Location: Sydney

You may like to consider the following alternatives, using a DO loop or array syntax to achieve what you want. I'm not sure if any is better than the other, as they all achieve a result.

IanLambley · Joined: 17 Dec 2006 Posts: 506 Location: Sunderland

Alternatively, if X is actually the array position, then you could just calculate an alternative array subscript to pull out the Y value as in:

Let
n = number of entries in original array "y"
i = new array position
j = equivalent array position in first array
Array y is dimensioned to n

JohnCampbell · Joined: 16 Feb 2006 Posts: 2615 Location: Sydney

Ian,

Your code reminds me of JDATE. (I'll understand that integer code one day.)

I'd prefer a simpler form of j=, possibly:
j = min (i, 2*n+1-i) ! valid for i in range 1:2n

or more simply you could use an IF

IF (i > n) then
j = 2*n+1-i
else
j = i
end if

I've been coming back to code I wrote years ago and now want it to be easier to understand. It saves time, especially if it needs changeing. Those old integer expressions are not easy to modify.

John

IanLambley · Joined: 17 Dec 2006 Posts: 506 Location: Sunderland

Well done John, it is getting simpler all the time. And yes, coming back to old code can be tricky. I think that good commenting is the answer. Once when a couple of us tried to delve into some Z80 assembler, written by someone else who had left the company, we found it was fully commented. Unfortunately one line of code was commented with the phrase "Old Indian trick" - very helpful I don't think.
Of course, you can point out that my miserable attempt avoided useful comments, but it was just intended to take the subject in another direction.

Actually, If you look at the original post, 10.8 is the first element in the input array and is required to be at the 10th and 11th position in the output, your equation does not do this inversion. It would need to be: