Dowload template

When facing chemical equilibrium problems of the type

it is often useful to construct logarithmic concentration versus pH diagrams to illustrate how the concentrations of the ions are dependant of the pH-value.

The theory behind the diagram is not too complicated and the construction is straightforward. However, generating nice looking diagrams can be time-consuming and tedious and therefore I wanted to share my excel template for generating dibasic log concentration – pH diagrams.

This template is intended for dibasic systems and can ideally be used for school assignments or teaching. The excel template will generate a diagram looking like the below example:

Any feedback is appreciated and can be left via the comment function below.

No need to bother with complicated field formulas and tedious chart formatting – that is already done for you!

Dowload template here

Only edit cells with green text to avoid breaking any formulas and functionality.

Dowload:

Swine flue cases in Sweden 2009 (click for larger image)

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Since my previous articles on boxplots in Excel, Improved advanced box-plot and whiskers chart in Excel and Box plot for Excel 2007, I have recieved a lot of questions on how to do boxplotswith negative values using Excel, since it would break the original method that I suggested.

There is a way, and I will guide you through it step by step. Let’s say you have the following data:

As you can see the boxplot (from the example found in Improved advanced box-plot and whiskers chart in Excel) is broken.

Now we need to trick Excel by adding an offset to your data so that all of them are in the positive range and show a “fake” y axis to make them appear in the negative range.

1. Add an offset to your data. Keep your offset in mind (lets pretend its 60 as in our example)

2. Create a dummy data series, with arbitrary values (though it’s practical if they are in the range of your real data).

The boxplot now looks a bit warped, like this:

3.  Now, move your 3 offset box-plot series to the secondary axis ( you will need to use the up/down arrow to select your invisible data series).

4. Set the scale on your secondary axis to appropriate fixed values (lets say 0 and 90 in our hypothetical example).

5. Set the scale on your primary axis to fixed values that are offset (subtracted) with the same value you used  to offset your boxplot data, in our example -60 and 30 (0-60 and 90-60 gives -60 and 30)

6. Hide the dummy series by making no fill and no line (right click -> format data series).

7. Hide secondary axis labels under (right click -> format axis).

Your boxplot should now look like this:

A “faked” boxplot showing data series with values in the negative range! Mission accomplished.

Version: Should work with any version. Tested with Excel 2007.

This article contain a quick tutorial on how to create a simple histogram in Excel 2007, to visualize for example student test score, like in the downloadable example.

Download example

To make this, start by creating a new worksheet and enter some structure, like in the image below.

Starting bin and bin width defines the resolution and span of the histogram categories. Data is the column where you will enter your data(!), in this caste test score results, Bin no is just a counter, Bins are the histogram categories, and Frequency is the number occurence of a test score result (Data) in Bins.

So how to achieve this? The key here is the frequency formula and the array formula function in Excel.

To enter an array formula this follow these steps.

1. Select the range that will contain your frequency distribution (in this case D6:D18)

2. Enter the frequency fomula in the toolbar text field:

=FREKVENS(B6:B65,D6:D18)

where B6:B65 should be the actual range containing your data.

3. After entering the complete formula press shift+CTRL+Enter to tell Excel you want this to be an array formula.

4. Done!

Now select the range containing your Bins and Frequency and create a clustered column chart. The default Excel column chart have a gap between the columns while traditionally in histograms there should be no gap between columns. Remove the gaps by right clicking the data series –> Format data series –> select  Alternatives for data series –> spacing –> set to zero.

Format the chart to your liking. A sample histogram can be seen below:

Another way to visualize distribution is by graphing the cumulative relative frequency. To do this, just create a new column where you sum up the relative frequencies for all bins. The sum will of course be 100%. Then create a new graph similar to the histogram above. The result can look something like this:

A couple of years ago I created a very simple QC-chart to keep track if instrument performance over periods of time. The chart fetches the usual data from user input and calculates average, upper and lower control and warning limits, and plots these data into an Individuals chart and a Moving average chart.

Once you have established the acceptable performance of your instrument/method, this makes it very easy to see if your method is performing poorly.

The baseline performance is usually established by collecting data over an extended time period, say one month, using some form of stable reference testing material. In the case of chemical analysis this can be a certified reference material (CRM) consisting of for example metal ions of a known concentration in a stable sample matrix.

Download: QC chart for Excel 2007 / 2003 (downloaded 5971 times)

The system extracts data by learning from a user’s selection of data they wish to capture into Excel. The more selections, the more the system is trained. An example scenario: You wish to import and track data from MSN’s weather page. Visit the site using the tool, enter Data Capture mode, and select a row or two of data from the table. Then click Select Similar, and the system will find similar data based on your previous selections.

The add-in is still in early beta so you test it on your own risk. I will get back to this add-in once I’ve had time to test it.

Keywords: Excel, chart junk, screencast, tutorial