David,

Everything in your formulation is providing satisfactory results ~ .7 percent compared to measured data. At first I had a problem but it was caused because of lack of scaling factor.

luke

In your previous case your data was in 256 rows with one column. Now it is in one row with 500 columns. Therefore your list structure is different. Please read up on list structures in Mathematica:

http://reference.wolfram.com/language/howto/WorkWithLists.html

The basic point is that the answer to your original question was tailored to the very specific data structure that your Excel import generated. If the dat structure changes then you need to modify your code accordingly to get the data that you need. In your new example it would be

dx = .12
dx (Integrate[
   Interpolation[data1[[1, 1]], InterpolationOrder -> 2][x], {x, 1, 
    500}])

Hi Luke, not sure why you are asking the same question again--perhaps a problem with the community interface? See my comments above.

Attached is a nb. where I'm trying to integrate a row of data from an imported Excel spreadsheet. In a previous attempt the formulation executed as expected but I was using 256 points (columns). However, when I went to 500 points the formulation failed to execute. Any suggestions?

Thanks

Luke

Attachments:

What one would do with a spreadsheet with additional information in it depends on what that data is and what you want to do with it. Each example case will be different depending on (a) the data and (b) what you want to do with the data.

A few comments which I think may help. The first one is that your expression

delta x = .12

should be

deltax = .12

I.e. no space between the delta and the x. (I realize that this is not used in your notebook to the point you showed, but you would probably use it in the next step.)

The second one is that your data1 parameter is a list that contains a list with the data you are interested in. I.e. it has the form

{
  {number, number, number....}
}

And you want to interpolate, not data1, but First[data1]. (The reason it is a list inside of a list is that when Importing form Excel, each sheet in the original spreadsheet it placed in a separate list so you can access each sheet as needed for a multiple sheet spreadsheet.)

Thus your integration expression should be

Integrate[
 Interpolation[First[data1], InterpolationOrder -> 2][x], 
{x, 1, 256}]

Note that I also changed the integration range. Remember in Mathematica that array indices start at 1, not 0. If you take a look at the interpolation expression's output by evaluating the following on its own

Interpolation[First[data1], InterpolationOrder -> 2]

you will see the assumed range of the interpolation in the formatted output.

So your integration ultimately will be,

deltax (Integrate[
 Interpolation[First[data1], InterpolationOrder -> 2][x], 
{x, 1, 256}])

I hope this helps...

Thanks for the help:Notebook attached

Attachments: