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#1
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calculate a point
I'm trying to calculate some steps or stages for a graph and am having
trouble, basically I'm trying to calculate a line between a point x,y to a point on a line between x1,y1 and x2,y2 that looks some like this: .x2,y2(8,6) / /-----------------------------------x,y(13,3) / .x1,y1(1,1) I think I got the slope 5/7=0.7142857, but I'm looking for the equation to calculate line between a point x,y to a point on a line between x1,y1 and x2,y. Go easy on me, I haven't been to school in 35 years. |
#2
Posted to microsoft.public.excel.charting
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calculate a point
On Jul 2, 4:30*am, Curbie wrote:
I'm trying to calculate some steps or stages for a graph and am having trouble, basically I'm trying to calculate a line between a point x,y to a point on a line between x1,y1 and x2,y2 that looks some like this: * * * * * .x2,y2(8,6) * * * * */ * * * * /-----------------------------------x,y(13,3) * * * / * * *.x1,y1(1,1) I think I got the slope 5/7=0.7142857, but I'm looking for the equation to calculate line between a point x,y to a point on a line between x1,y1 and x2,y. Go easy on me, I haven't been to school in 35 years. Start from slope = (y - y1)/(x - x1) = (y2 - y1)/(x2 - x1). From this we get the equation you want - y = y1 + (x - x1)*(y2 - y1)/(x2 - x1). In the above case, the equation is y = 1 + (x - 1)*(6 - 1)/(8 - 1) or. if you really need to simplify this y = 2/7 + 5/7*x xt |
#3
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calculate a point
On 01/07/2011 17:30, Curbie wrote:
I'm trying to calculate some steps or stages for a graph and am having trouble, basically I'm trying to calculate a line between a point x,y to a point on a line between x1,y1 and x2,y2 that looks some like this: .x2,y2(8,6) / /-----------------------------------x,y(13,3) / .x1,y1(1,1) I think I got the slope 5/7=0.7142857, but I'm looking for the equation to calculate line between a point x,y to a point on a line between x1,y1 and x2,y. Go easy on me, I haven't been to school in 35 years. If you mean to a point half way between x1,y1 and x2,y2, that point is at (x1+x2)/2, (y1+y2)/2, or at 4.5, 3.5. If, on the other hand, you mean your line to be horizontal, i.e. y=3, then your point would have an x value of x1+(x2-x1)*y/(y2-y1), or 1+7*3/5. David Biddulph |
#4
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calculate a point
On 06/07/2011 08:48, David Biddulph wrote:
On 01/07/2011 17:30, Curbie wrote: I'm trying to calculate some steps or stages for a graph and am having trouble, basically I'm trying to calculate a line between a point x,y to a point on a line between x1,y1 and x2,y2 that looks some like this: .x2,y2(8,6) / /-----------------------------------x,y(13,3) / .x1,y1(1,1) I think I got the slope 5/7=0.7142857, but I'm looking for the equation to calculate line between a point x,y to a point on a line between x1,y1 and x2,y. Go easy on me, I haven't been to school in 35 years. If you mean to a point half way between x1,y1 and x2,y2, that point is at (x1+x2)/2, (y1+y2)/2, or at 4.5, 3.5. If, on the other hand, you mean your line to be horizontal, i.e. y=3, then your point would have an x value of x1+(x2-x1)*y/(y2-y1), or 1+7*3/5. David Biddulph Correction: .... x1+(x2-x1)*(y-y1)/(y2-y1), or 1+7*2/5. David Biddulph |
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