Can I Plot Log (x) with Error Bars without Changing err_x Values?

[Lorna]

Hello,

I have a column of 'x' values, each with an error 'err_x' serving as error bars.

My question is: If I need to plot 'log(x)', Do I need to make any changes to 'err_x' to reflect the log operation before plotting them as error bars ?

Thank you in advance

Lorna

 

[CRGreathouse]

I would plot log(1 + error) for positive error and -log(1 - error) for negative error. That way error is on the same scale.

 

[Lorna]

What is the significance of the '1' ? and why not just log(error)?

 

[CRGreathouse]

What is the significance of the '1' ? and why not just log(error)?

Why don't you pick some errors in -1 < e < 1 and see for yourself?

 

[Lorna]

Thank you, althought I still don't understand why "1" not another number

 

[CRGreathouse]

Thank you, althought I still don't understand why "1" not another number

It's the only number that will make the error bars tend to 0 as the error approaches 0. With a smaller value very small errors won't show up at all (calculation error trying to take a negative log); with a larger value errors won't ever get closer than a certain distance from the point no matter how small the errors are.

 

[Lorna]

Now I see. Thank you SO MUCH!