[Gnuplot-info] getting the time value for time series data From: Andy S. - 2007-03-03 00:00 ```I have a question, which if the answer is "you can't do that", might be a suggestion: Let say I have a data file with some time data: 2004 11 1 100.0 2005 1 15 90.2 2005 3 28 60.4 2006 4 15 23.8, etc I do: set xdata time set timefmt "%Y %m %d" p "data" us 1:4 Now I define a function: f(t) = a * exp( -(t - t0) / tc) I can fit with this function, and over plot the fit with: p "data" us 1:4, f(x) In the above, the function is called with the time in seconds. But now I wish I could plot the residuals. The thing I tried first: p "data" us 1:4, "" us 1:(\$4 - f(\$1)) This produces a plot, but f() is called with just the year - not the time is seconds. I wish there was some way to get the x time value. Is there already a way? - I was unable to puzzle one out... Two possible syntaxes that I've thought of: allow "\$x" in a using expression to evaluate to the time (and \$y if "set ydata time" is in effect") p "data" us 1:4,"" us 1:(\$4 - f(\$x)) of define a function, xtim (and ytim), which could be called with the data file line number if it needs to have an argument p "data" using 1:4,"" us 1:(\$4 - f(xtim(\$0))) Comments? Thanks, Andy S. ```
 Re: [Gnuplot-info] getting the time value for time series data From: - 2007-03-04 14:52 ```Andy S. wrote: > I wish there was some way to get the x time value. Is there > already a way? - I was unable to puzzle one out... The thing you're looking for is the timecolumn() function. It works just like column() (which you know best in its shorthand form, \$1), but tries to figure out time/date data, too. ```