Sunday, November 24, 2019

Profile Analyzer


Roasters often want to analyze their roasts to measure consistency, look for aspects of the profile that can be improved, and to create metrics to score the roast against a set quality measures.  Artisan offers many ways to provide information on a roast.  These include the Statistics Summary, Plotter and Math tabs, AUC (area under the curve), and many others.

Artisan v2.1 adds a new set of features to provide additional insights.  These features continue Artisan's heritage of exploring new ways of interpreting roast data.

The Analyzer is a combination of several new tools.  The first is a new curve fit tool.  While it is similar to the Math tools that were introduced in Artisan many years ago, the Analyzer is greatly enhanced.  The Analyzer can compute and fit three different mathematical curves to a profile's BT curve.  The computed curve fit BT is placed in the background along with the curve fit RoR (ΔBT).  The computed curve is then compared to the profile's BT curve.  A summary table is presented that provides detailed information about the quality of the fit.  The Analyzer can also compare the profile's BT to any given background curve.

 

An Example


Let's look at an example before going into more detail.  We will fit the BT curve below to an x² curve.  To simplify things the ET curve is not shown, the background curves are shown in red and have been widened to be more visible.

Note: Use Config > Colors to change a curve's color and click the little graph icon on the navigation toolbar to change the width of a curve.
 

Notice that this profile has an existing background curve that will be replaced by the fit curve.  Don't worry, your original file is not touched.  Artisan will warn and guide you if you try to save on top of your original file.


Note: The first time the Analyzer is run the result boxes will probably be on top of each other and the graph.  Simply drag them to another position, Artisan will remember where you placed them.
 
There are several things to notice when the Analyzer finishes.  Two boxes display the results.  More about those later.  A grey mask highlights the region over which the curve fit was performed. There is an inner masked area that indicates the interval of interest over which all the metrics calculations are performed. The start time of each region can be set on the Config > Curves > Analyze tab.  The end of both regions is always the DROP time.

Note: Depending upon the color theme in use, especially for darker themes, the analysis mask areas may be easier to see by unchecking Config > Phases > Watermarks.


The upper box in the screen shot shows a table of curve fit results.  Remember that in this example we fit the BT to an x² curve.  That means the curve fit RoR will be a straight line.  The MSE BT value is a measure of how closely the profile compares to the linear (straight line) RoR.  A perfect match between the profile BT and the curve fit BT would show a MSE of zero.  Larger numbers indicate a less precise match.  A description of each column will be found later in this article.

The lower box provides metrics that indicate the severity of flicks and crashes in the profile.  Each line in the table is a segment of the profile RoR (ΔBT) throughout the interval of interest.  A segment starts and ends when the RoR crosses the curve fit RoR.  In this example the first segment begins at 07:08.  The time 07:08 is when the interval of interest begins. The RoR at this time is below the curve fit RoR.  At 08:12 the RoR crosses the curve fit RoR beginning the second segment.  The third segment starts at 09:54 when the RoR again crosses the curve fit RoR.  The right most column, ABC/secs, is the area between the curves divided by the number of seconds.  This is a good indicator of flicks and crashes.  The second and third segments show ABC/secs larger than 1.0 indicating noticable flick and crash.

Note: The Analyzer always calculates and reports using Celsius.

Segments


Let's look at another example to see how the analyzer combines segments to make analysis easier.  Segments start and end when the profile RoR crosses the curve fit RoR. Sometimes they are short in duration or small in amplitude.  The Analyzer will automatically combine such segments with the one to the left (earlier) based upon the Analyze Options on the Config > Curves> Analyze tab

In the example below, which was fit to an x² curve, the BT RoR goes above and below the curve fit RoR several times. 


Notice that the Segment Analysis table shows 5 segments.  Looking at the curves there are more more times the profile RoR crosses the fit RoR.  The Analyze Options used for this analysis regards 3 or fewer samples as not significant and a difference between the two RoR curves of 0.6 as not significant.  As a result the analyzer has combined some segements to the left. Look now at the third segment that begins at 08:04.  It has a Max Delta of -0.61. This is just above the Delta Threshold of 0.6 (the threshold is an absolute value).  If the setting is changed to 0.61 the following table results.  This is a good setting for this profile.



To see all of the segments set both Analyze Options to zero.  The table below shows all the segments.


Auto All


The Auto All option on the Tools>Analyze menu will fit three different curves to the profile BT.  It fits x², x³, and ln() curves.  The x² fit will be displayed in the graph after Auto All has completed.  The curve fit results for all three fit types will be shown in the Curve Fit Analysis box.  The results are sorted in ascending order of MSE BT.  The Segment Analysis box will show results for the x² fit. 


Fit to any chosen background


The Analyzer can compare the profile BT to any background curve.  Be sure the desired background BT is displayed in the graph and choose "Fit BT to Bkgnd" from the Tools > Analyze menu.


Description of the Fields

 

Curve Fit Table Fields:


First column : The curve fit type.

MSE BT : The mean square error (difference) between BT and the curve fit BT. The closer to zero the better the fit.

RoR Δ @FCs : The difference between BT RoR and curve fit RoR at first crack start time. 

Max+/Max- RoR Δ : The maximum arithmetic difference between BT RoR (ΔBT) and curve fit RoR.  The Max+ is the greatest difference when BT RoR is above (greater than) the curve fit RoR.  The Max- is the greatest difference when BT RoR is below (less than) the curve fit RoR. 


Segment Table (crash and flick) Fields:


Start : Start time of the segment.

Duration : Length of the segment in mm:ss.

Max Delta : The maximum difference between actual RoR and fit RoR for the segment.

Swing : The difference between the previous segment's Max Delta and this segment's Max Delta.

ABC/secs : The Area Between the Curves divided by the number of seconds in the segment.  The Analyzer calculates the area between the BT RoR and the curve fit RoR for each segment and divides that area by segment number of seconds.  This value is indicative of the severity of a flick or crash. The closer to zero the better.

Optional settings (Config>Curves>Analyze tab)

 

Curve Fit and Interval of Interest Options


Start of Curve Fit Window : This is the time when the curve fit begins. The curve fit will be performed using the BT data from this time until DROP.

Custom offset seconds from CHARGE : If "Custom" is chosen for Start of Curve Fit Window, the curve fit will start this number of seconds _after_ CHARGE.


Interval of Interest Options


Start of Analyze interval of interest : This is the time when the interval of interest begins. Calculations and results from the Analyzer are performed starting at this time and ending at DROP.  The Start of Analyze interval of interest must not be earlier than Start of Curve Fit Window.  If it is set earlier a warning message will be displayed when running the Analyzer.

Custom offset seconds from CHARGE : If "Custom" is chosen for Start of Analyze interval of interest, the interval of interest will start this number of seconds _after_ CHARGE.


Analyze Options


Number of samples considered significant : When performing segment analysis the Analyzer combines short segments that are not considered significant.  If a segment is this number or less samples it will automatically be combined with the previous segment.  This setting is shown below the Segment Analysis table with the label "Samples Threshold".

Delta RoR Actual-to-Fit considered significant : When performing segment analysis the Analyzer combines segments where the profile RoR is near to the fit RoR for the duration of the segment. If the absolute value if the difference between the profile RoR and the fit RoR is this value or less the segment will automatically be combined with the previous segment. This setting is shown below the Segment Analysis table with the label "Delta Threshold".



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