# Logarithmic axes and grids

themadmathematician shared this idea 11 years ago
Under Consideration

Just to remind everyone it is still on the wishlist... :-)

http://www.geogebra.org/for... 1

x-axis log only, y-axis log, or semi-log

In science and engineering, a semi-log graph or semi-log plot is a way of visualizing data that are changing with an exponential relationship. One axis is plotted on a logarithmic scale. This kind of plot is useful when one of the variables being plotted covers a large range of values and the other has only a restricted range – the advantage being that it can bring out features in the data that would not easily be seen if both variables had been plotted linearly.

Because of the nonlinear scaling of the axes, a function of the form y=ax^b will appear as a straight line on a log-log graph, in which b will be the slope of the line (gradient) and a will be the y value corresponding to x = 1.
There are many pages of commenting on logarithm axes.

Tony 1

Hi,

If I have y^2 = 2 ln(x) + 3 and wish to plot it linearly as Y = m X + c,

ie where Y = y^2 , and X = ln(x) with the gradient of the line being m (and m = 2) and the vertical intercept being c = 3.

Can we have change of variables for the axes so that the vertical axis is Y (which is y^2) and the horizontal axis is X (which is ln(x)) and the graph becomes a straight line.

Am parking my feature request for changeable variables for axes in this thread as I see request for log - log or semi log axes here is relevant.

lewws 1

log-log and semi-log are a request from a scientific and engineering perspective...BTW, the log should be available in any base although the only common one is for common logarithms, base 10.

It would be an excellent pedagogical tool for many.

Tony

BTW, Lewis, your method works, but from experience the actual grids are more convincing to the student. 1

Don't expect this anytime soon - it would be a massive job as all objects would have to know how to draw themselves on the new coordinate system so it's not a priority. 1

We will be patient, as we know the current push is to complete 4.2 for September.

Thanks for your consideration of this concept...

Tony 1

It would be enough for me if this feature was available only in the regression/data analysis window. In that way it would not affect all objects.

Regards

Mikkel 1

I'm pushing this to the top (once more) with a new suggestion.

I understand, that it is very hard to implement this feature globally but one solution would be to introduce a new graphics view in which you can only a very limited number (i.e. finctions and points) of objects visible. In this graphics view it should then be possible to have axes and grads with a logarithmic scale.

Once again I'm crossing my fingers.

Best regards,

Mikkel 1

I think the previous suggestion was great - implement it in the 2-variable regression window. When copied to the Graphics window logarithmic axes are lost, but this does not matter since all interesting analysis (i.e. visually ensuring linearity) has already taken place. 3

Hi,

the 2 var logarithmic regression is "almost done", unfortunatelly there are some bugs blocking the release. 2

Is it still "almost done"? :-)  2

That sounds great! 2

I do not believe it makes sense to expect a a square or rectangle object to "draw itself" on a log scale. Usually if we want to draw a rectangle on a log plot we still want it to look like a rectangle, we do not want to distort the sides of the rectangle to look like log curves.

If we want log plots, it makes more sense to plot the log of the function and just relabel the axes so they show log values i.e.

Instead of the axes labels showing (-2, -1, 0, 1, 2, 3) they show show (0.01, 0.1, 1, 10, 100, 1000) or the exponential form which is more compact (10^-2, 10^-1, 10^0, 10^1, 10^2, 10^3). In either case, this could be done by simply allowing the axes labels to be more flexible both in what they show and in their formatting. 2

Just reminding everyone again. ;-) 1

Still not there, are we? 1

Is this feature still in beta?