Trendline

[Juan Pablo Gallardo]

I have always wondered, how do I replace the following formula to get the value of y?

Like what is the formula in Excel for this so that if I replace x=23 I get y for example?

[#2]

Replace each x with the cell address containing the value for y, e.g. A2 then to get the power, replace the numbers with ^ followed by that number. Also, in Excel a formula starts with the equal sign:

=-0.0008*A2^6+0.0605*A2^5+ ......

[#3]

@Jan Karel Pieterse Thank you, yes I have done that but the result is a number completely out of the curve, it does not make any sense.

[#4]

@Juan Pablo Gallardo 

Click on Format Trendline (or box with the formula) and in formatting assign 17 decimal places, not 4 as you have now. Try formula again with updated parameters.

[#5]

@Sergei Baklan no difference at all.

[#6]

@Juan Pablo Gallardo 

How trendline formula looks after you changed the number of decimals?

[#7]

@Sergei Baklan  the numbers have more decimals, but they are decimals, negligent enough to make a change on the final value.

[#8]

@Juan Pablo Gallardo 

Yes, they are decimals, but decimals which significantly affect calculation result.

[#9]

You are quite correct. This also means that you have to be careful in taking the fitted line seriously, small inaccuracies in the fit have huge effect on the outcome of predictions. This asks for careful statistical analysis.

[#10]

@Jan Karel Pieterse 

What's interesting, during the week there were 5 or so questions about trendline formula accuracy. And no one for years before, at least not in my memory.

[#11]

Must be people trying to make sense from Corona data :)

[#12]

My son pointed me to this xkcd which is illustrative for this discussion.
https://xkcd.com/2048/

[#13]

@Jan Karel Pieterse 

Thanks to your son!