# Logarithmic axis / grid

ethunder123 shared this idea 11 years ago
Under Consideration

I would like to have the possibility to switch the axes to a logarithmic scale.

At school we work with funktions that describe different electric circuits, like RC-circuit (Resistor-Capacitor).

These functions can be drawn as a "Bode plot" which need a logarithmic scale on the x-Axis.

At the moment I use the Curve-funktion of GeoGebra to make the x-Coordinate logarithmic. (See attached file).

But this is not the best solution: You can't really work with this "curves". For example it is not possible to create points of intersections and so on. Also the numbers on the axis need to be modified with text boxes.

I think an integrated funktion to switch the axes (and also the grid) would help here much. https://ggbm.at/543939 1

Me too. Logaritmic graphs would be an wonderfull new feature. I think this request have being asked for earlier.

Hovewer, a straight line between two points would not be a straight line anymore. 1

You may want to use g(x)=f(10^x) instead of Curve. It allows you to create points on g etc (but labels on x axis do not match). 1

Find your suggestion very interesting .

Would appreciate very much if you would explain why you replace x by 10^x and how this will effectively make logarithmic scale on the xAxis. Would be helpful if it can be illustrated in ggb file. Thanks very much  1

You may want to use g(x)=f(10^x) instead of Curve. It allows you to create points on g etc (but labels on x axis do not match).
If there is need for logarithmic Y-axis, that doesn't work.

Forgot to say, there should be possible to select logarithmic scale on BOTH X and Y-axis. Also, it would be nice if the base was possible to change. That is other numbers than just 10 and e. 1

As an algebra teacher, I agree that being able to switch the X-axis and/or Y-axis to a logartihmic axis with a logarithmic grid with be really helpful in teaching logarithms and exponents. This would be a great feature for algebra teachers. 1

I agree that there should be a choice of grid divisions for each axis much like the Cartesian, polar, and isometric systems. I think that what I would like to see is in addition to the distance drop down menu in each of the axes tabs, is a drop down that has

fraction

degree trig

common log

natural log

possibly log of other common bases

The distance drop down could be linked to this for divisions.

As you can see, I feel that this is an excellent idea. I do not believe it will be too easy however.

Tony 2

It won't be hard to add such feature if GeoGebra was yet another graph plotting program. But GeoGebra is a dynamic geometry + algebra system, which means it has to deal with circles, conics etc. I can't imagine how to make these work together with logarithmic grid. 1

I do not see why logarithms cannot be implemented as that is just a way to scale a Cartesian coordinate axis; however, could the other features be added as they are methods of scaling within the Cartesian coordinate plane. We are not really interested just another graphing plotting program, but it would be nice to have an easy way to apply the scale when needed. I do not think that it needs to be in another category like Cartesian, polar, and isometric. It just needs to be an optional scale that could be used quickly within Cartesian coordinates. Most log graphs use the Cartesian plane

In Algebra, it is nice to show students that logarithmic functions actually graph as straight lines rather than curves. Also, in engineering there are many applications that use standard-log and log-log graphs for advanced work. This type of graph paper is standard fair in many engineering courses. {I had to have it in my course work.}

In science and engineering, a log-log graph or log-log plot is a two-dimensional graph of numerical data that uses logarithmic scales on both the horizontal and vertical axes.

This is just a request that many would like to see implemented, unfortunately, it has been too many years for me to remember specific uses for log and log-log graphing. I am sure that there is some active mathematician or engineer that could give much better reasoning as to why it would be nice to implement. Even if it needs to wait until Beta 5.

Tony 1

It won't be hard to add such feature if GeoGebra was yet another graph plotting program. But GeoGebra is a dynamic geometry + algebra system, which means it has to deal with circles, conics etc. I can't imagine how to make these work together with logarithmic grid.
I guess some features (you mentioned) must be deactivated while axis is non-linear. 2

If you want to see how function f(x) looks with logarithmic scale, then

1) use g(x) = f(10^x) if you need x-axis to be logarithmic

2) use g(x) = log(f(x)) if you need y-axis to be logarithmic

3) use g(x) = log(f(10^x)) if you need both axes to be logarithmic 1

Bonjour ,

cette demande a déjà été faite il y a 5 ans .

J'en conclus que ce ne doit pas être évident à implémenter .