Help with excel and logarithmic scales

philip · 12-31-2003, 06:09 AM

I've been searching for an hour now and I can't seem to find an answer to my problem with excel. I want to make a graphic with a logarithmic scale with base 2 on the y-axis. Is this possible and could you give me a few pointers to what values I have to enter in the properties of the axis to make this happen. I suspect I have to add an exponent or logarithm as values for minimum and maximum, but I can't think of anything for the primary and secondary unit. It's for a line diagram.

If it's not possible in excel do you perhaps know a free program that can draw this kind of graphics.

Thanks for the help!

Thoran · 12-31-2003, 09:26 AM

Log scale is easy... just create the graph using the wizard, then select the axis you want log, right-click to bring up the menu and select properties for that axis... Log is a checkbox on one of the tabs.

Base 2... well that's a different animal. What exactly are you trying to do? I don't believe you'll be able to automatically do that, I've never seen anything in Excel that would lead me to believe that it can deal easily with binary numbers (other than converting to decimal and back). You might be able to fake it though since log scale will yield major ticks that are 1, 10, 100, 1000... (works in any base) Make sure to shut off minor ticks (since there'll be 10 of those and you only want two) and figure out how to scale your points so they appear in the right position on the axis (should be pretty straightforward).

[ 12-31-2003, 09:36 AM: Message edited by: Thoran ]

philip · 12-31-2003, 10:33 AM

Quote:

Originally posted by Thoran:
Log scale is easy... just create the graph using the wizard, then select the axis you want log, right-click to bring up the menu and select properties for that axis... Log is a checkbox on one of the tabs.

I could do that as well.

Quote:

Base 2... well that's a different animal. What exactly are you trying to do? I don't believe you'll be able to automatically do that, I've never seen anything in Excel that would lead me to believe that it can deal easily with binary numbers (other than converting to decimal and back). You might be able to fake it though since log scale will yield major ticks that are 1, 10, 100, 1000... (works in any base) Make sure to shut off minor ticks (since there'll be 10 of those and you only want two) and figure out how to scale your points so they appear in the right position on the axis (should be pretty straightforward).

I'm trying to put the concentration of a medicine in blood in a graphic for a maths assigment. The problem is that it are small numbers, I need from the scale from 1 to around 16 not much more. I'll try your suggestion, though I might be quicker off with just drawing them by hand. I already wrote a program that'll calculate all the numbers.

I tried a bit with I need a few numbers between 10 and 20, no metter what I do with the different variables I can choose in Excel it'll always put 100 as maximum (instead of say 20), and if I try to adjust the numbers for the scale it says that the units in the log scale can only be 10 so that I'm stuck with 1,10,100 whch is way too large for what I need

Thanks for the help!!!

Thoran · 12-31-2003, 10:52 AM

oh... I see now... you don't need a binary graph, you just need to change the graph extents. You can set the min/max/zero crossing for all axes in the properties dialog for that axis (same dialog that allows you to set log scale). Piece of cake!

philip · 12-31-2003, 11:07 AM

No, that's the problem, if I enter the numbers I want, so 1 to 20, it automatically goes to 1 to 100, which is too big. Neither can I change the other scale units (the size of the steps) it immediately goes to 10 with the message that logarithmic scales only use those numbers (at least M$ logarithmic scales [img]tongue.gif[/img] ).

Thoran · 12-31-2003, 12:25 PM

right... log scale forces limits to a power of 10, those boneheads.

well, it's cheeze but what I'd do is stretch the graph until it's REALLY TALL, then I'd use paint shop pro to do a screen capture of the bottom section of the graph since now it's big enough to show a decent amount of detail from 0-20. Embed the image of the graph in my paper and I'm done.

philip · 12-31-2003, 03:50 PM

I'm going for drawing instead. Though it's really annoying, everytime I want something it's M$ knowing better that I actually don't want it. Philip: log scale is 2. M$: No you don't want that, cause we know log scales are always 10.

Just as annoying as the automatic paragraphs and lists. Though I could turn that off [img]smile.gif[/img]

Night Stalker · 12-31-2003, 06:26 PM

Excel only does Log base 10 and I think natural log.

If you are into Math and engineering, I'd suggest you get a copy of MatLab from The Mathworks Co. Prentice Hall publishes a Student guide and demo for about $50US. There are only very minor differences between the student version and the pro version. (The pro version is $2000++++ dependion on add on libraries)

MatLab is widely known as the "engineer's spreadsheet". It is vector based math, and can handle complex math (imaginary numbers) as well. There isn't a math problem you won't be able to do (though the student version is limited in matrix size - the limit is more than enough to do classwork.) The school labs may already have it.

philip · 12-31-2003, 07:22 PM

Thanks for the suggestion. It's only for a one0time project so I want it to be free.

12-31-2003, 06:26 PM	#8
Night Stalker Lord Ao Join Date: June 24, 2002 Location: Nevernever Land Age: 49 Posts: 2,002	Excel only does Log base 10 and I think natural log. If you are into Math and engineering, I'd suggest you get a copy of MatLab from The Mathworks Co. Prentice Hall publishes a Student guide and demo for about $50US. There are only very minor differences between the student version and the pro version. (The pro version is $2000++++ dependion on add on libraries) MatLab is widely known as the "engineer's spreadsheet". It is vector based math, and can handle complex math (imaginary numbers) as well. There isn't a math problem you won't be able to do (though the student version is limited in matrix size - the limit is more than enough to do classwork.) The school labs may already have it. __________________ [url]\"http://www.duryea.org/pinky/gurkin.wav\" target=\"_blank\">AYPWIP?</a> .... <img border=\"0\" alt=\"[1ponder]\" title=\"\" src=\"graemlins/1ponder.gif\" /> <br />\"I think so Brain, but isn\'t a cucumber that small called a gherkin?\"<br /><br />Shut UP! Pinky!

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12-31-2003, 06:09 AM	#1
philip Galvatron Join Date: June 24, 2002 Location: aa Posts: 2,101	I've been searching for an hour now and I can't seem to find an answer to my problem with excel. I want to make a graphic with a logarithmic scale with base 2 on the y-axis. Is this possible and could you give me a few pointers to what values I have to enter in the properties of the axis to make this happen. I suspect I have to add an exponent or logarithm as values for minimum and maximum, but I can't think of anything for the primary and secondary unit. It's for a line diagram. If it's not possible in excel do you perhaps know a free program that can draw this kind of graphics. Thanks for the help!

12-31-2003, 09:26 AM	#2
Thoran Galvatron Join Date: January 10, 2002 Location: Upstate NY Age: 56 Posts: 2,109	Log scale is easy... just create the graph using the wizard, then select the axis you want log, right-click to bring up the menu and select properties for that axis... Log is a checkbox on one of the tabs. Base 2... well that's a different animal. What exactly are you trying to do? I don't believe you'll be able to automatically do that, I've never seen anything in Excel that would lead me to believe that it can deal easily with binary numbers (other than converting to decimal and back). You might be able to fake it though since log scale will yield major ticks that are 1, 10, 100, 1000... (works in any base) Make sure to shut off minor ticks (since there'll be 10 of those and you only want two) and figure out how to scale your points so they appear in the right position on the axis (should be pretty straightforward). [ 12-31-2003, 09:36 AM: Message edited by: Thoran ]

12-31-2003, 10:52 AM	#4
Thoran Galvatron Join Date: January 10, 2002 Location: Upstate NY Age: 56 Posts: 2,109	oh... I see now... you don't need a binary graph, you just need to change the graph extents. You can set the min/max/zero crossing for all axes in the properties dialog for that axis (same dialog that allows you to set log scale). Piece of cake!

12-31-2003, 11:07 AM	#5
philip Galvatron Join Date: June 24, 2002 Location: aa Posts: 2,101	No, that's the problem, if I enter the numbers I want, so 1 to 20, it automatically goes to 1 to 100, which is too big. Neither can I change the other scale units (the size of the steps) it immediately goes to 10 with the message that logarithmic scales only use those numbers (at least M$ logarithmic scales [img]tongue.gif[/img] ).

12-31-2003, 12:25 PM	#6
Thoran Galvatron Join Date: January 10, 2002 Location: Upstate NY Age: 56 Posts: 2,109	right... log scale forces limits to a power of 10, those boneheads. well, it's cheeze but what I'd do is stretch the graph until it's REALLY TALL, then I'd use paint shop pro to do a screen capture of the bottom section of the graph since now it's big enough to show a decent amount of detail from 0-20. Embed the image of the graph in my paper and I'm done.

12-31-2003, 03:50 PM	#7
philip Galvatron Join Date: June 24, 2002 Location: aa Posts: 2,101	I'm going for drawing instead. Though it's really annoying, everytime I want something it's M$ knowing better that I actually don't want it. Philip: log scale is 2. M$: No you don't want that, cause we know log scales are always 10. Just as annoying as the automatic paragraphs and lists. Though I could turn that off [img]smile.gif[/img]

12-31-2003, 07:22 PM	#9
philip Galvatron Join Date: June 24, 2002 Location: aa Posts: 2,101	Thanks for the suggestion. It's only for a one0time project so I want it to be free.

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