Sign of y Axis Labels

Hi,

The simplest way that does not alter the underlying data is offset the traces.  Go to the trace modify dialog and look at the offset and set the y multiplier = -1.

Bam!

Andy

Hi Andy,

 Thank you for your reply. If I understand correctly what you are suggesting is to use the command: ModifyGraph muloffset={0,-1} . However, when I tried this, it flipped the y curve but left the labels intact. Is there something I am missing?

Best,

Hi,

If the original wave had y values that were all negative, then the -1 multiplier would flip them to positive albeit in a mirror image.  The test data I had did show this effect and the corresponding tick labels also reflected the change in sign. Here is my example.  Note the Y axis is now showing an "unnatural" direction with increasing going down.  This retains the shape of the curve, though I would probably not reverse the axis myself.

Note: when I did the -1 multiplier the tick labels represented now positive numbers.

Andy

Hi Andy,

Thank you again. I am sorry, but this is not quite what I would like to achieve. Specifically, I do not want to modify the values of the original  y-wave (because that would change many other things). For example, for a figure of a typical spectrum shown below, I am simply looking for a "cheap" way to remove the minus sign of the numerical values of the y-axis labels by simply modifying the labels. I was able to reproduce your example only by multiplying the original y-wave with "-1" which changes the values of the original data (which is analogous to the procedure I described in my original post which I would like to avoid).

Best,

Hi,

I did not create a new wave, just used trace offset multiplier = -1 and then reversed y axis scale. Compare my graph 1 to 3. I think it does what you want.

Andy

Hi Andy,

It looks like I am missing something. When I followed your instructions this is what I obtained:

It looks like at this stage, I need another step to change the limits of the y-axis by using the negative limits of the original plot's y-axis. I could get these limits using GetAxis.

Not quite what I expected but I think this should work.

Thank you!

Good,

Glad to be of some assistance.

Andy

just for the record here is the function which accomplishes my original goal following Andy's suggestions:

Seem like you got the solution, but I would like to just mention that things do not need to get that complicated (and some other random notes which might be of help to you).

You could just call ModifyGraph muloffset={0,-1} once for the whole graph to reverse all traces at once.

It seem you have multiple y-axes with a manual range. In the case of autoscaling the axes everything would adjust automatically and you could call SetAxis/A/R axisName to reverse the axis.

Your code might fail if you have a 'top axis'. Change this if you want to make the function a bit more robust: y_axes_list=removefromList("top;bottom;",axislist(GraphName))

Also, function code in Igor is terminated with just 'end', not 'end function' (this is no error per se, however; any stuff after end is ignored).

I would like to offer a different solution, not necessarily better. It does involve creating two new waves, a label position wave and a label text wave.

First, bring up the Modify Axis dialog for the Y axis. On the Auto/Man Ticks tab, select User Ticks from Waves. In the User Tick Waves box, click the New From Auto Ticks button. Click Do It.

You now have a graph that looks exactly like it did before, but you have a couple of new waves. If you edit the new text wave to remove the minus signs, you will have achieved a lying axis!