EEasley Posted November 10, 2011 Share Posted November 10, 2011 Hi- I am adding scatter data to a GTPlot reaction path that I created in REACT. I would like to include error bars on the scatter data, but I am not sure how to go about adding the standard deviations in the spreadsheet. I have already calculated the standard deviation of each analyte in Excel for major cations and anions, and then I am using the reported standard deviation by GeoTech, who rents the multimeter I used to measure field pH and temperature. Basically, I would like to simply add that the pH has a standard deviation of +/- 0.2 pH units and that temp has a standard deviation of 0.15 degrees C. Is there a simple way to just add in the standard deviation, or do I have to enter the standards and measured values in the GSS spreadsheet (as described in the user guide). My main concern is that I am only using reported standard deviation values from the equipment provider for pH and temperature, as I didn't run any calibrations myself (but now I am thinking I should have!). Please let me know if you have any suggestions! Thanks! Elisabeth Easley Quote Link to comment Share on other sites More sharing options...
Brian Farrell Posted November 10, 2011 Share Posted November 10, 2011 Hi Elisabeth, All you need to do to set errors bars is enter a triplet of values separated by vertical bars in each cell of your GSS spreadsheet. For pH, put in 6.3|6.5|6.7, for example, to create error bars of standard deviation 0.2 about a measured pH value of 6.5. Unfortunately you cannot just enter a standard deviation value once and have it apply for all your datapoints. This may be a bit tedious, but that is how the program is set up right now. Hope this helps, Brian Farrell Aqueous Solutions LLC Quote Link to comment Share on other sites More sharing options...
EEasley Posted November 11, 2011 Author Share Posted November 11, 2011 Hi Elisabeth, All you need to do to set errors bars is enter a triplet of values separated by vertical bars in each cell of your GSS spreadsheet. For pH, put in 6.3|6.5|6.7, for example, to create error bars of standard deviation 0.2 about a measured pH value of 6.5. Unfortunately you cannot just enter a standard deviation value once and have it apply for all your datapoints. This may be a bit tedious, but that is how the program is set up right now. Hope this helps, Brian Farrell Aqueous Solutions LLC Hi Brian- Thanks. I was able to calculate the standard deviation as you described above. I'm not having any success in getting the error bars on an XY plot though...is there a setting that I am missing?? I made sure that the sample points were small enough so that they wouldn't overlap the margin of error, but the actual error bars don't show up. I tried plotting an XY of pH vs Temp in the original GSS spreadsheet, and also as scatter data on a reaction path GTPlot of pH vs temp, but no error bars. Thanks for your help! Elisabeth Quote Link to comment Share on other sites More sharing options...
Brian Farrell Posted November 11, 2011 Share Posted November 11, 2011 Hi Elisabeth, Can you post your GSS and React files so I can take a look at your problem? Thanks, Brian Quote Link to comment Share on other sites More sharing options...
EEasley Posted November 11, 2011 Author Share Posted November 11, 2011 Hi Elisabeth, Can you post your GSS and React files so I can take a look at your problem? Thanks, Brian Attached are the GSS and React files. Thanks. EE Waunita Mixing Smpl 2.rea Nov pH T with ST DEV.gss Quote Link to comment Share on other sites More sharing options...
Brian Farrell Posted November 14, 2011 Share Posted November 14, 2011 Hi Elisabeth, Your problem was that you didn't put the range of values for each sample in a single cell. I've made you a GSS spreadsheet that will show you how to enter in your data. You'll want a row for each analyte (pH and Temperature) and columns for each sample. You can enter in three values in a single cell, separated by a vertical bar (|), to represent the data point itself and the ends of the error bar. If you enter in two values separated by a double bar (||) you will get just the error bar. Of course, entering a single value per cell will give you a standard data point. Hope this helps, Brian Nov pH T with ST DEV.gss Quote Link to comment Share on other sites More sharing options...
EEasley Posted November 14, 2011 Author Share Posted November 14, 2011 Hi Brian- Got it. Yes, it is quite tedious to plot the errors in this manner for large datasets! Do you forsee any addition to the program that incorporates a more simple function for plotting errors? When you are using geochemical data to verify or support reaction path models, it is nice to have the error bars, however it is a little too time consuming to plot them in this way for large datasets that include 20+ analytes that each have an associated error! Thanks very much for your help, I really really appreciate it! Best, Elisabeth Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.