Semi-log paper

[Gamewizard]

Hi, does anyone know how to plot data on semi-log graph paper ?

 

i have no idea, i read on a website but its not clear.

 

Can someone please explain to me? or give me a website link

 

thanks

[swansont]

It's just like plotting on regular graph paper, except the exponential function goes on the log axis; the major lines will be factors of 10 different from each other. Take care to pay attention to the minor lines, since they also have nonlinear spacing.

[AlphaSheeppig]

As you move away from the origin on the log axis, there's a big gap between the first line and the second, but the gaps get smaller and smaller... After the 10th grid line, the pattern repeats... Importantly, the origin does not represent zero sice log(0) is undefined, so starting with the origin, number the lines 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400 and so on... Make sure the major grid lines (the ones just before the biggest gaps) are numbered in increasing powers of 10, (i.e. 1, 10, 100, 1000, etc...)

 

You can just scale it to fit your data if you need to (eg. if the lowest number in your data is 0.00035, you'd number the origin as 0.0001).

 

After that, it's just like normal graph but with weird spacing...

[Gamewizard]

As you move away from the origin on the log axis, there's a big gap between the first line and the second, but the gaps get smaller and smaller... After the 10th grid line, the pattern repeats... Importantly, the origin does not represent zero sice log(0) is undefined, so starting with the origin, number the lines 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400 and so on... Make sure the major grid lines (the ones just before the biggest gaps) are numbered in increasing powers of 10, (i.e. 1, 10, 100, 1000, etc...)

 

You can just scale it to fit your data if you need to (eg. if the lowest number in your data is 0.00035, you'd number the origin as 0.0001).

 

After that, it's just like normal graph but with weird spacing...

 

Ok, where exactly is the origin? is that where the 1 is ? I have numbered the major grid lines, the top one is 1000, then 100, then 10, and the last one 1, is that right do u think ? the paper i am using has 3 cycles..

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and if my data was something like 5505390, 13722390, and 27417338 , where abouts would i plot them on the graph ?

 

thanks

[AlphaSheeppig]

Yes, that's right. The origin is (usually) the bottom left point on the graph, so the bottom line should be 1.

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and if my data was something like 5505390, 13722390, and 27417338 , where abouts would i plot them on the graph ?

 

thanks

 

OK... multiply the 1, 10, 100 and 1000 by a million to get the right scale. Then the 5505390 would be plotted two thirds of the way between the 5th and sixth lines above the 1 million. 13722390 would be plotted a bit above halfway between the 10 million line and the one above it and so on...

[Gamewizard]

Yes, that's right. The origin is (usually) the bottom left point on the graph, so the bottom line should be 1.

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OK... multiply the 1, 10, 100 and 1000 by a million to get the right scale. Then the 5505390 would be plotted two thirds of the way between the 5th and sixth lines above the 1 million. 13722390 would be plotted a bit above halfway between the 10 million line and the one above it and so on...

 

Ok , i did that and i have got 1000, 000,

10,000,000,

100,000,000,

1000, 000, 000,

 

is that ok do you think ?

[John Cuthber]

Or, you could take the log of the data and plot it on ordinary graph paper.

[Gamewizard]

Ok , i did that and i have got 1000, 000,

10,000,000,

100,000,000,

1000, 000, 000,

 

is that ok do you think ?

 

 

Thank you so much for your help at last i understand

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Or, you could take the log of the data and plot it on ordinary graph paper.

 

 

 

I would if i could, but unfortunately I need to learn how to plot on semi-log paper as have a test on it.