Creating equation to match a graph curve

[jackson_]

In order to find the exact area under this curve, I need an equation so that I can use the formula. I was wondering if there was a way to create an equation that follows the entire graph curve or even just multiple equations covering different parts.
I need to calculate the total area under the spike shaped graph lines, above the red line if that makes sense. However a start would just be being able to find an equation.
Any help would be appreciated.

 

[khansaheb]

In order to find the exact area under this curve, I need an equation so that I can use the formula. I was wondering if there was a way to create an equation that follows the entire graph curve or even just multiple equations covering different parts.
I need to calculate the total area under the spike shaped graph lines, above the red line if that makes sense. However a start would just be being able to find an equation.
Any help would be appreciated.
View attachment 36527

In order to find the exact area under this curve

It is almost assured that you will not be able to find the area exactly - you could only estimate.

What have you learned regarding "estimation"?​

What would be the average height of the spikes above the red line.​

 

[Steven G]

Do you have any points for this function? Where did this graph come from.
Personally I think that if you had the function, then you could easily calculate the area.

 

[jackson_]

It is almost assured that you will not be able to find the area exactly - you could only estimate.

What have you learned regarding "estimation"?​

What would be the average height of the spikes above the red line.​

One method I tried was using the trapezoidal rule. The average height above the red line is 74.7

 

[jackson_]

Do you have any points for this function? Where did this graph come from.
Personally I think that if you had the function, then you could easily calculate the area.

All the dots on the line are points from an excel table. The 'x' axis is hours and the 'y' axis is the concentration of a substance in the blood stream after that many hours. There is no function however.

 

[BigBeachBanana]

All the dots on the line are points from an excel table. The 'x' axis is hours and the 'y' axis is the concentration of a substance in the blood stream after that many hours. There is no function however.

They look almost identical. I would try to fit a function for one of the troughs and multiply. If you provide the data, I can attempt to find a polynomial fit.

 

[blamocur]

One method I tried was using the trapezoidal rule. The average height above the red line is 74.7

1. Isn't trapezoidal rule enough for your purpose? Did you consider more more accurate methods of numerical integration?
2. The red line is at y=100 -- how can the average height be 74.7 ? Do you mean 100 + 74.7
3. The part of your graph above the red line is almost periodic, especially if you ignore the first spike. When I see periodic graphs my favorite approach is to look at Fourier series.