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I have problem to draw in Mathematica a plot like this:

Plot[{Sum[a^10*(-1)^(x-a), {a, 1, x}]}, {x, 1, 10}]

The problem is that on the plot there is no graph. As it can be calculated, there should be some values plotted. When I try to draw this equation in Mathematica as

plot (sum(a^10*(-1)^(x-a),a=1 to x)), x = 1 to 10

everything works fine, so I think I did something wrong with the first command in Mathematica, but I can't find the mistake.

Dr. belisarius
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Ziva
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1 Answers1

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Plot has attributes, HoldAll, so the Sum isn't evaluated,

try this:

Plot[Evaluate[Sum[a^10*(-1)^(x - a), {a, 1, x}]], {x, 1, 10}]

Where the sum evaluates to:

Mathematica graphics

before plotting:

enter image description here

related questions/answers:

Plot draws list of curves in same color when not using Evaluate

How and when to use Evaluate?

Behavior of expression evaluation in Plot

I prefer a different domain:

Plot[Evaluate[Sum[a^10*(-1)^(x - a), {a, 1, x}]], {x, -3, 2}]

Mathematica graphics

Community
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s0rce
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  • Yeah, that's it – Dr. belisarius Dec 05 '13 at 03:34
  • @s0rce I have one more problem when i Want to draw this: Plot[Evaluate[Sum[Binomial[x, l]l^10(-1)^(x - l), {l, 0, x}]], {x, 1,2}], no graph is plotted, and I can't notice way, because if I will calucate this, there should be some points – Ziva Dec 06 '13 at 00:35
  • @Ziva the result of your sum seems to be only defined for integers. – s0rce Dec 06 '13 at 04:35
  • @sOrce, Yes, you are right! I forgot to restrict x to integers. – Ziva Dec 06 '13 at 10:25