Graphing Data Using Kaleidagraph



Graphing Data Using Kaleidagraph

Standard spreadsheet programs are adept with plotting data. However, specialized programs offer advanced graphing functions and are often a little easier to use for plotting. Kaleidagraph is a program designed primarily for plotting data. It lacks many of the spreadsheet capabilities. However, it does allow formula entry similar to Microsoft Excel.

Kaleidagraph has an interface which looks like the figure below.

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Figure 1 – Kaleidagraph Interface

You’ll notice that it has the standard grid window similar to Excel but it also has a Formula Entry window. For an example of using formulas, we will again convert from the temperature in Celsius to Kelvin. To define the column, double click on the A in the top of the column. This will bring up the following window.

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Figure 2 – Column Format

You can then enter the column label. In this case, type in Temp (C), and select OK.

Now do the same for column B, but label it Temp (K). Enter in the following data in the Temp (C) column: 45, 50, 65, 75, 85. After entering in this data, Kaleidagraph has already calculated some statistics such as the average (mean) and standard deviation. You can view these by clicking Functions(Statistics. For the Temp (K) column, we can have all the values calculated by clicking the Formula Entry window and specifying the following formula: c1=c0+273.15. The notation refers to the column (c) and the number is the actual number of the column which is in the square box at the top of the column. When the formula entry is complete, click Run. The Temp (K) column is now filled in.

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Figure 3 – Result of Formula Entry

Note that in Figure 3, the formula necessary is visible to the right.

Plotting the Data

To plot data, you will select Gallery and then you will have a variety of options available from the drop down menu. We will be using Gallery(Linear(Scatter. This will bring the following window up.

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Figure 4 – Plotting Definition Window

Here you will define the x and y variables by clicking the circle next to the appropriate choice. In this case, let’s select the Temp (C) as the x variable and Temp (K) as the y variable. Then click New Plot. You should then see the following plot.

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Figure 5 – Resultant Plot

Unlike Microsoft Excel, you can insert the degree symbol for the Temp (C) axis label by double clicking on the Temp (C) label and it will bring up a window for editing it.

Now for curve fitting the data, you will select Curve Fit. For our purposes, you will then want to select Linear. A window will appear for you to select the data to curve fit. The y-variable will be shown and you will need to select it by clicking the box next to it and then clicking Ok. A line will now appear through the data points along with an equation of the line with an R or R2 value. However, you may customize the line options by clicking Format(Curve Fit Options. Here you can select for the line to be forced through zero (for calibration curves a necessity) and also for the R2 value to be displayed. This is advantageous because it tells you how good the line fits your data. The closer the R2 value is to 1, the better the fit. The resultant plot is obtained.

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Figure 6 – Curve Fit

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