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#1
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Need some plotting help - determining which points are farthest apart
Hello,
I am working on a spreadsheet to simulate some measurements to see which ones work the best, how many samples should be taken, etc. Very early on in this endeavor, so bear with me please ;) I have two columns, a13:a112 and b13:b112 with labels of 'Xi' and 'Yi' respectively. The cells in each column contain a formula '=norminv (rand(),0,1)' to generate random X & Y values with a mean of '0' and a SD of 1, with the intent of creating a bivariate normally distributed plot. So far this part seems to be working pretty well. I copied that formula into both columns, and copied down 100 rows so I should have 100 (x,y) coordinates that are randomly generated every time the spreadsheet recalculates. From that, I'm trying to calculate several different values - mean radius (MR), radial standard deviation (RSD), and center-to-center distance (D). Of the three, the c-t-c measurement *seemed* like it'd be the simplest - it surely is the easiest one to measure in 'real life'; simply measure the distance between the two furthest apart points on the plot (easily identified visually), and voila, you have c- t-c. Doing that in terms of a formula in Excel has me stumped for the time being. No real problems with the MR & RSD calcs, so this is doubly frustrating. What seems to be tripping me up is determining which points are the ones furthest apart. The actual calculation once they are identified is fairly simple. The problem is that for one iteration the two furthest apart points could be xmax and xmin, then the next time they could be ymax and ymin, and the next time they could be somewhere else entirely on a diagonal. Any hints as how to reliably determine the two points that are furthest apart would be very much appreciated. Thanks, Monte |
#2
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Need some plotting help - determining which points are farthestapart
Excel 2007
Max distance between x, y points: http://www.mediafire.com/file/1nxka0k5kyb/05_22_09.xlsx |
#3
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Need some plotting help - determining which points are farthestapart
Herbert Seidenberg wrote:
Excel 2007 Max distance between x, y points: http://www.mediafire.com/file/1nxka0k5kyb/05_22_09.xlsx I opened this with E2003. Am I correct that the orange area is supposed to be the distance calculated between points? If so, it doesn't make sense as there are too many zeros. Is something lost in the translation? |
#4
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Need some plotting help - determining which points are farthestapart
Smartin:
Since we want combinations, not permutations, half of the array has been set to zero with the term (c_1 Rc_2 C) (using R1C1 ref designations) The diagonal is zero by definition. I am using features of Excel 2007 that do not easily translate into Excel 2003. |
#5
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Need some plotting help - determining which points are farthestapart
Herbert Seidenberg wrote:
Smartin: Since we want combinations, not permutations, half of the array has been set to zero with the term (c_1 Rc_2 C) (using R1C1 ref designations) The diagonal is zero by definition. I am using features of Excel 2007 that do not easily translate into Excel 2003. Ah! Makes sense. Thanks for the explanation. If I could engage you a little further, is the use of complex numbers a convenience, or could this have been accomplished just as well using the "usual" way of computing the distance between points =sqrt((y2-y2)^2+(x2-x1)^2) ....Never mind, I think I answered that one myself. Ok, what's confusing me is the R1C1 syntax. Any pointers? |
#6
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Need some plotting help - determining which points are farthestapart
Smartin:
I prefer R1C1 because 1. All the formulas in the array appear the same. 2. The formulas are shorter. 3. That's what MultiPlan used. Check the A1 Option and check out the mess. |
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