Export image data precision

Question

I'm sure there is a very easy way to control this, but I have been searching for an hour now without luck.

I plot a function and export it to get a table that I can use in TikZ.

Plot[{AiryAi[x], AiryBi[x]}, {x, -20, 10}]
Export["airyfunctions.dat", %]

The resulting .dat file has numbers with about 16-17 digits (e.g. 4.044732860029933) whereas I'd like them to have about 5 digits of precision.

Also, the table currently separates the coordinates from the plot like: {x_1,y_1}, {x_2,y_2}, {x_3,y_3}. I'd prefer if they were formatted instead with spaces x_1 y_1 and newlines. I tried using "FieldSeparators" -> " " without luck.

Answer 1

I haven't used TikZ, so I don't know how you can deal with the exported data by Export["xxx.txt",data] in TikZ directly. At least, the data exported in this way cannont be used in Origin, because the txt file exported directly as you did, in fact, is the InputForm of plotting the curve in Mathematica.

So, it is necessary to pretreat the Plot result. I do it as follows:

data = Flatten[
   List @@@ Select[Flatten[List @@ graph], (Head[#] == Line) &], 2];

where graph is the curve you want to export.

After the pretreatment, use Export["xxx.txt",data,"Table"], and the data will be formatted with spaces and new lines as you wish. But you can only export the two graphs separately.

As for the precision, I cannot figure it out, either. Maybe, after export, using Excel to deal with the precision of exported data is an alternative.