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Equation: Exponential growth. Previous topic Next topic, No expanding text in this topic, Print this topic, Feedback on: GraphPad Curve Fitting Guide - Equation:. Bacterial cells, if a growth curve for the conditions used has already been established. This is the most common method used to rapidly estimate bacterial numbers. Other methods, such as viable plate counts, can also be used for determining bacterial growth curves but.
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A variable undergoing logistic growth initially grows exponentially. After some time, the rate of growth decreases and the function levels off, forming a sigmoid, or s-shaped curve. For example, an area's population increases at an exponential rate until limiting factors slow the growth. Eventually, growth stops altogether. All logistic functions take the form of N divided by the sum of 1 and Ae raised to the power of negative kx, where N, A, e and k are all constants. Excel calculates values following logistic growth and can chart them on a line graph.
1.Type '=A1/(1+B1exp(C1D1))' without quotes into an Excel cell.
2.Type the value of the function's 'N' constant into cell A1. For example, if you want to chart the growth function, type '1,800 ÷ (1 + 5,000 × e^-0.07x)' without quotes, where 'e' is the mathematical constant equaling 2.71828; enter '1800' into cell A1.
3.Type the value of the function's 'A' constant into cell B1. With this example, enter '5000' into cell B1.
4.Type the value of the function's 'k' constant into cell C1. Continuing the example, enter '0.07'
5.Enter the lowest value of 'x' that your graph will track in cell D1. For example, if you will begin tracking the function at the graph's origin, type '0' into cell D1.
6.Enter a function into cell D2 that describes the increments you want on your graph. For example, if the function tracks periodic population growth in a culture, where 'x' represents minutes, and you want to estimate the population every 20 minutes, type '=D1+20' without quotes into cell D2.
7.Highlight the bottom right corner of cell D2. Click your mouse and drag this corner downward, extending the formula downward and producing the x-axis values for your chart.
8.Repeat the previous step with the cell where you entered your formula. This produces your chart's y-axis values.
9.Highlight the values that the previous step produced. Click 'Insert' in Excel's menu bar.
10.Click 'Line' from the ribbon's 'Charts' tab. Select one of the '2-D Line' thumbnails that the drop-down box displays. Excel will plot your function's logistic growth on a chart.
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About the Author
Ryan Menezes is a professional writer and blogger. He has a Bachelor of Science in journalism from Boston University and has written for the American Civil Liberties Union, the marketing firm InSegment and the project management service Assembla. He is also a member of Mensa and the American Parliamentary Debate Association.
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![Curve Curve](https://i.ytimg.com/vi/k9YO1TLyCVk/maxresdefault.jpg)
Related Articles
- 1 Subtotal Columns in OpenOffice
- 2 Insert Tangents in Excel
- 3 Create a Descriptive Statistics Table in OpenOffice
- 4 Use Excel to Interpolate
A variable undergoing logistic growth initially grows exponentially. After some time, the rate of growth decreases and the function levels off, forming a sigmoid, or s-shaped curve. For example, an area's population increases at an exponential rate until limiting factors slow the growth. Eventually, growth stops altogether. All logistic functions take the form of N divided by the sum of 1 and Ae raised to the power of negative kx, where N, A, e and k are all constants. Excel calculates values following logistic growth and can chart them on a line graph.
1.Type '=A1/(1+B1exp(C1D1))' without quotes into an Excel cell.
2.Type the value of the function's 'N' constant into cell A1. For example, if you want to chart the growth function, type '1,800 ÷ (1 + 5,000 × e^-0.07x)' without quotes, where 'e' is the mathematical constant equaling 2.71828; enter '1800' into cell A1.
3.Type the value of the function's 'A' constant into cell B1. With this example, enter '5000' into cell B1.
4.Type the value of the function's 'k' constant into cell C1. Continuing the example, enter '0.07'
5.Enter the lowest value of 'x' that your graph will track in cell D1. For example, if you will begin tracking the function at the graph's origin, type '0' into cell D1.
6.Enter a function into cell D2 that describes the increments you want on your graph. For example, if the function tracks periodic population growth in a culture, where 'x' represents minutes, and you want to estimate the population every 20 minutes, type '=D1+20' without quotes into cell D2.
7.Highlight the bottom right corner of cell D2. Click your mouse and drag this corner downward, extending the formula downward and producing the x-axis values for your chart.
8.Repeat the previous step with the cell where you entered your formula. This produces your chart's y-axis values.
9.Highlight the values that the previous step produced. Click 'Insert' in Excel's menu bar.
10.Click 'Line' from the ribbon's 'Charts' tab. Select one of the '2-D Line' thumbnails that the drop-down box displays. Excel will plot your function's logistic growth on a chart.
References (2)
Resources (2)
About the Author
Ryan Menezes is a professional writer and blogger. He has a Bachelor of Science in journalism from Boston University and has written for the American Civil Liberties Union, the marketing firm InSegment and the project management service Assembla. He is also a member of Mensa and the American Parliamentary Debate Association.
Cite this Article