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This makes a bar chart okay
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But not such a good area chart
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We can create a table that splits the positive and negative values
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but the result is disappointing
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The areas simply go to zero at the next value, which is not what we want. This happens even when the Excel Time-scale X axis type is selected by going to Chart..Chart Options..Axes and selecting "Time-scale". However, Time-scale has one feature that lets us easily fix the problem. Unlike the ordinary category axis, it does not present values in the same order as they appear in the table, but in strict time order. So if we make a new set of rows below our first set
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where the formulae are (left to right, assuming the original table header started at cell A1)
=IF($A2*$A3>0,NA(),$A2)
=IF($A2*$A3>0,NA(),$B2+($B3-$B2)*$A2/($A2-$A3))
=IF($A2*$A3>0,NA(),0)
=IF($A2*$A3>0,NA(),0)
then the two areas should meet the zero line at the same interpolated date!
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Remember, this only works if you've selected the "Time-scale" option in Chart Options. If you're looking for more Excel help, see the Jon Peltier and Andy Pope links on the right.