Unable to Draw Custom Curve on Semi-Log Scatter Plot with X-Axis Dates

[Kirsten Gustafson]

Hi,

I have a scatter plot on which I would like to draw my own curve fit. The plot is semi-log, with dates along the x-axis.

I am having difficulty developing an equation that shows up on the graph. After some failed trial and error with adding aCustom Curve, my next idea was to begin by copying the equation fromthe automatic Straight Line Fit, to ensure that the equation I am using would generate a line in the general area of the plot where I want the final line, then I could manually tweak the Custom Curve equation to get the final trend I want.

Below I have included a screenshot to illustrate what I have tried: I have use the Straight Line Fit to generate the equation Log10(y) = 131.22 + 2.01E-16*X. However, when I enter this same into a Custom Curve equation, no line is drawn on my graph (Yes, I have ticked the tick box to check :)). Are there adjustments that need to be made in the Curve expression for the semi-log plot

Something else suspicious: When the Curve Draw curve I have generated is selected in the Visible Lines and Curves menu, all of the options underneath Label and Tootip... button are greyed out (Include in axis range, Update manually, One per Color, etc). This leads me to believe that Spotfire does not like the equation I have entered and it not calculating it at all, despite the fact that theStatusbox below theCurve expressionsays OK.

Can anyone advise I am at a loss for what else to try. For reference, I am using v. 7.6.0.61. Thanks!

[Jason Alley 2]

A couple things. I don't know if the custom curve draw will work with your x-axis being a date column.

May have to normalize it to number of months and then but brackets around x.

131.22 + 2 E-16 * [x]

[Kees van Ojik]

A hint to the problem is already visible in the function plotted in the graph, namely it is assuming a logarithmic function now log(y)=F(x)

 

Try putting in following function:

 

log10(131.22 + 2.01E-16*X)

 

 

[Jeff Grunschel]

Is this the answer  I tried using brackets around "x" and it didn't change anything.  I'm pretty sure the brackets are only necessary for names that are not SQL friendly.