Re: [libreoffice-users] chart help

At 00:54 25/01/2014 -0500, James Lockie wrote:
> I have 2 questions related to charts.  Say I have 2 columns: date 
> and value  2 Rows "Jan, 1" and "Mar 3".
>
> Q1. I want the x-axis to increment by month.
> Q2. I want to only display the x-axis labels for the data points I have.

I don't this problem is particularly well defined.  You mean the 
first of January and the third of March - right? - not January 2001 
(or 1901?) and March 2003?  Do you want your January and March values 
to be located for their month generally (as if for the Ides of March, 
maybe) or for their actual dates?  You say you will have some months 
missing, but what happens if you have two entries for one month?

When you say that you want the horizontal axis to "increment by 
month", I imagine you are referring to the axis labels, not the way 
the chart behaves.  The point of the axis of  a chart is to 
distribute the values according to some domain.  In this case, this 
could be date or perhaps month.  (These are slightly different, since 
with dates, January and March would be slightly closer than February 
and April.)

If you have a proper chart with a horizontal time domain (whether 
date or months), I think you should reconsider your request to 
suppress labels for months that are not represented by data.  The 
point of axis labels is to show the domain that is spread along that 
axis, not to label the data points.  You should have regularly spaced 
axis labels and just enough of them to make reading the chart 
convenient.  If you need to make a feature of which months are 
represented, you can do this by separately labelling the data points 
(or chart bars or whatever) themselves.

Alternatively, you can treat the data as non-parametric.  This is 
what you do when there is no measurable domain.  You would do this if 
your data were, for example, for dog breeds, where there would be no 
obvious order or measurable comparison.  Would Chihuahuas come before 
or after Pekinese?  Is a Labrador two or three times a Yorkshire 
Terrier - or more?  There is no answer to these questions (though I 
suspect some dog owners would offer one!).  In that case, your months 
would be individual events, probably in the right order but equally 
spaced instead of in any meaningful way.  If your third data point 
was for April, for example, the separation of April from March would 
be the same as that between January and March - not half of it.

If you went the non-parametric route, you would have to convert your 
dates to plain text first.  Beware that you cannot do this merely by 
formatting the date column to MMM, say, as the real date would still 
be in the cell and would be used by Calc in creating your 
chart.  Instead, use something like =TEXT(A1;"MMM") to create a text 
copy of the month name and prepare your chart from these values instead.

I trust this helps.

Brian Barker


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