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Help with Slope Functin in Excel

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    Help with Slope Functin in Excel

    Hello, I am a new user so please forgive me if I fail to include anything.

    When using the 'SLOPE' function in Excel 2007, is the returned value in degrees, percent or radians? Below is an example:

    Column A (Y-values)

    2359.7546
    2359.6244
    2359.4944
    2357.1235
    2356.7319
    2356.4566
    2355.6608
    2355.2594

    Column B (X-values)

    0.0000
    0.5208
    0.5814
    5.6406
    5.7726
    7.6469
    11.7451
    13.3342


    When I use the function " =SLOPE(A1:A8;B1:B8) " I get the following result: -0.349. Is this number reported in degrees, percent, or radians?

    Assuming that the value is not in degrees but simply an angle, I then use the function " =DEGREES(-0.349). The result from this function is -20.

    Am I correct in interpreting this value (-20) as being the slope in degrees?

    Does this seem to be a correct way of converting the original slope value into degrees or am I wrong? Any help would be appreciated.

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    Re: Help with Slope Functin in Excel

    It is not in degrees. It the conventional measure of slope.
    Quote Originally Posted by Excel Help
    The slope is the vertical distance divided by the horizontal distance between any two points on the line, which is the rate of change along the regression line.
    For example, the line containing the two points (0,5) and (1,10) has a slope of 5.
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    Re: Help with Slope Functin in Excel

    The SLOPE function returns the slope value for a line.

    y = m*x + b

    m being the slope of the line. So, m = -0.349. Since your line is starting at 0, b would be equal to 2359.7546. To find some value for y, plug in the m and b values and solve for y with some value of x.

    y = (-0.349) * x + 2359.7546

    The slope is a unit of y/x. "Rise over run".

    Am I correct in interpreting this value (-20) as being the slope in degrees?
    In short, no.

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    Re: Help with Slope Functin in Excel

    Additionally, the function DEGREES converts radians to degrees, but you don't have radians.

    I would find it very unusual to need to express a slope as degrees. If that is what you really, really need to do, then you want

    =DEGREES(ATAN(SLOPE(A1:A8;B1:B8)))

    The slope of a line is the same as the tangent of the angle of the line with the x-axis. The arctangent function will take a tangent and return the angle in radians. DEGREES will convert radians to degrees.

    But it would be unusual to need that.

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    Re: Help with Slope Functin in Excel

    Well... Looks like I'm too slow. But here's your numbers graphed. The answer is no. It's rise over run.
    Attached Files Attached Files

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    Re: Help with Slope Functin in Excel

    Thanks for all of the insight. Yes, i see that I was leaving a step out (not using the ATAN function). Thanks bluerog for the spreadsheet. It helped me see where i was going wrong.

    So, as I understand it, using the SLOPE function simply returns the rise/run value for x and y. It is essentially a unitless measure. That is, the unit of measure is determined from the units for x and y.

    If I want to report the value in degrees, I would need to use both the ATAN and DEGREES function, respectively, to get the slope reported in degrees?

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    Forum Moderator 6StringJazzer's Avatar
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    Re: Help with Slope Functin in Excel

    Quote Originally Posted by LSUArkFan View Post
    So, as I understand it, using the SLOPE function simply returns the rise/run value for x and y. It is essentially a unitless measure. That is, the unit of measure is determined from the units for x and y.
    Correct; people don't normally use units for it, but you could express it in terms of the units for y over units for x.
    If I want to report the value in degrees, I would need to use both the ATAN and DEGREES function, respectively, to get the slope reported in degrees?
    Correct. Although I would be curious as to why you would want it in degrees.

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    Re: Help with Slope Functin in Excel

    Thanks for all of the help 6StringJazzer. I understand the rise/run formula and it makes sense to me. My reason to want to convert to 'degrees' is simply for ease of understanding. For example, the data that I originally posted gives a slope value of -0.349. Now, if the result were to be something like "30 degrees" I could have a better idea as to what that would look like. As it stands, I have difficulty visualizing/understanding exactly what a slope of -0.349 or the absolute value 0.349 looks like.

    A second reason that I am trying to convert to degrees is that it is for some graduate research that I am working on. As can be seen from my previous posts, I'm still a-bit unsure as to how Excel is actually calculating. I want to understand what is actually going on within the program. I don't want to just submit numbers and get results without knowing how they were derived.

    I hope that my response wasn't too long winded. Again, thank you for the suggestions/information regarding slope.

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    Re: Help with Slope Functin in Excel

    Quote Originally Posted by 6StringJazzer View Post
    Correct; people don't normally use units for it, but you could express it in terms of the units for y over units for x.
    Correct. Although I would be curious as to why you would want it in degrees.
    Just to add my perspective, I do work where there are operational limits based on degrees of terrain slope, so it's handy to be able to easily determine a generalized terrain slope based on meters of rise and run.

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