how to make graph y range 0-180-(-180)-0?

[Marbak]

I'm using the openoffice calc to create some graphs displaying the change in an angle, however it is desirable to never go higher then 180 degrees, so that instead of 0-360 it's 0 0 -> 180 -> (-180) -> 0

I would like the graph's y axies to go from 0 - 180 > -180 - 0, so in other words from 0 degrees, to 190 then switch into negative 180 and from negative 180 go back to 0. Is it possible to manipulate the graph to do this?

[jrkrideau]

[Marbak]

I'm probably explaining this a bit poorly, the data does of course give the appropriate values. And I know I can change the axis scales. if it was from -180 to 180 through 0 that would be easy. The problem is that it's not, the axis is from 0 to 180 directly to -180 to 0.

So that the axis would look like this:

deg
0----- |
-90---|
-180-|
180--|
90----|
0------|________________________Hz

What this really is, is 360 degrees, but it's not desirable to use values above 180 in this case. The actual degree value will be shifting between 160 - 200 degrees which is turned into 160 - (-160) degrees instead. If using a normal -180 - 180 scale this will give a wrong appearance as it goes between the two without ever passing the values between 160 and -160,

[jrkrideau]

I am lost. Any chance that you can point to a similar graph (any software inplementation) to show what you need.

At the moment I just don't see how you go from -180 to 180.

[Marbak]

The use is with electric alternating currents, they're displayed as waves. Measuring the input wave versus the output wave revealing the lag (not sure if lag would be the appropriate term, English isn't my native language) in the current. When right on top of each other it's 0 degrees. When the output is shifted slightly to one side of the input it will gain a positive lag of x degrees, the other way gives a negative x degrees.

If shifted to the point where the output is the opposite of the input it will be 180 degrees.
if shifted a whole 'round' making it 360 degrees it's 0 degrees. It's completely uninteresting if it's actually 360 degrees, 720 degrees or anything like that, it's just considered 0 degrees. just the difference between the two on one cycle that's of importance.

With this logic 180 degrees, is the same as -180. When watching a wave which will probably be the thousandth cycle or more of a current you can't see if it comes before or after as all you see are two continuous waves.

This also makes it so that 200 degrees may just as well be -160 degrees, 100 degrees just as well be -160 degrees. It's waves not circles or physical degrees. Because of this it's desired to only use -160 - 160 degrees, not 0 - 360. Therefore at a point it will go from -> 180 to -180 -> ( ... 178 > 179 > 180/-180 > -197 -198 ...)


With a capasitor or/and coil in a circuit it will add this lag depending on the frequency of the input, it's to display how the circuit's lag change depening on the frequency. This one shifts with x degrees around the area of 180 degrees. so for example 175-(-175) which could be said as 175-185 in which case it's more obvious that the line shouldn't run through the area between 175 to 0 to -175. But again, it is desirable to use negatives over values higher then 180.

Right now I have to 'cheat' using actual values of 0-360, then hide the scales on x axis with some solid text block or similar where I add the corresponding negative values of those above 180. Would like to not have to do that though

[ken johnson]

You could add a dummy series then use its category labels to take the place of the normal 0 to 360 degree y axis labels.
http://www.mediafire.com/view/?td5ec31orvmu6v1
In the above attached doc (Dummy series for unusual y axis labels.ods) the chart has two data series.
The first is a plot of columns A and B.
The chart's y axis Scale has been altered from Automatic to Minimum = 0, Maximum = 360, and Major interval = 30 (to match the spacing of the values in column D). The y axis' labels have had their format changed from General (same as Source) to three semicolons (;;;). This format code renders the usual y axis labels invisible.
The second is a plot of columns C and D with column E included as the category values.
The second series' line is changed to invisible and its Markers have been removed. Also, the second series is set up to include its data labels and those labels are set to show only the Category with Placement equal to Left.
You should notice that the column E label values each have a trailing space character. This separates the new y axis labels from the tick marks for a better appearance.
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[jrkrideau]

[quote]English isn't my native language)

[Marbak]

Thank you, that to be what I need.

[ken johnson]

The original Y axis labels can also be hidden by right-clicking the y axis, choosing "Format axis..." from the popup menu then removing the tick from the "Show labels" check box on the "Labels" tabsheet of the "y Axis" dialogue.
I knew there had to be an easier way than using the ";;;" format code. It had slipped from my mind.

Ken Johnson
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