How do I convert a linear scale array to a logarithmic without getting negative values?

Hi All

I need to plot ( bar plot) values, and on the X axis , I want to convert them to logarithmic, but the values <1 become negative. how to avoid and fix it ?

[Rik]

You would have to remove those.

Answer 1

[madhan ravi]

Replace < 1 with nan.

[farzad]

this is what I do , I take the log immediately when I am plotting I doubt I can do what you say, how do I do that ?

f=barh(y, log(x), 'basevalue', min(x));

[Rik]

f=barh(y, max(0,log(x)), 'basevalue', 0);

If you want to replace values, you will have to store the intermediate result, or write a function that does that.

[farzad]

thank you very much for your answer. yes this is right but : I think something is wrong.

Because : here we are actually taking the logarithm of the X axis values. so if the maximum is 10^ 4 , the max on the logarithmic will be 4.

but I meant only changing the scale of showing the values , therefore , not touching the actual X values, but changing the X values. the same way it is done in Excel.

[Rik]

You can change the axis if you like. What exactly do you want to happen?

[farzad]

please see the attached. the distances of the lines is in logarithmic scale. this is how you can do in Excel :

[madhan ravi]

 set(gca, 'XScale', 'log')

[farzad]

Thank you ! it worked on scaling , but all the bars disappeared ! I wanted to use the log scale to see the small bars better !

[Rik]

In X or Y?

[farzad]

the scaling should be only along X, cause the bars are along X axis

[farzad]

Any opinions on why the bars disappear ? the divisions start from 10^-1 to 10^4 and I should have a graph in this range

[farzad]

any ideas ?

[madhan ravi]

Nope

[farzad]

That's a pity, I'm stuck

[farzad]

ریک, do you have any suggestions?