Blog Archives

RFishBC CRAN Release

November 22, 2018
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RFishBC CRAN Release

I am pleased to announce that the RFishBC package has been released to CRAN. This package is intended to help fisheries scientists gather age and measurement data from digital images of calcified structures and, possibly, back-calculate p...

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New FSA Authors

November 3, 2018
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It was always my hope that the Fisheries Stock Assessment (FSA) R package would become a community endeavor. With the recent release on CRAN of v0.8.21 that hope has finally come to fruition. This version has two new co-authors. Alexis Din...

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Testers for RFishBC

June 6, 2018
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Back-calculating lengths of fish at previous ages from measurements made on calcified structures (scales, otoliths, etc.) is fairly common practice within some fisheries agencies and institutions. The FishBC software distributed by the Amer...

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Adding Zero Catches

April 18, 2018
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Introduction Much of my work is with undergraduates who are first learning to analyze fisheries data. A common “learning opportunity” occurs when students are asked to compute the mean catch (or CPE), along with a standard deviation (SD), across multiple gear sets for each species. The learning opportunity occurs because some species will invariably not be caught in some gear...

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Collapsing Categories or Values

March 29, 2018
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Introduction I have received a few queries recently that can be categorized as “How do I collapse a list of categories or values into a shorter list of category or values?” For example, one user wanted to collapse species of fish into ...

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Stock-Recruitment Graphing Questions

December 12, 2017
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Stock-Recruitment Graphing Questions

A fishR user recently asked me In the book that you published, I frequently use the stock-recruit curve code. The interface that shows both the Ricker/Beverton-Holt figure with the recruit per spawner to spawner figure (i.e., the dynamic ...

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Plots of Back-Calculated Lengths-At-Age I

November 7, 2017
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Plots of Back-Calculated Lengths-At-Age I

Last spring, I posted about my version of a modified age-bias plot. One reader commented on that post via Twitter – “Now that you solved the age-bias plot, how about the ‘best’ display of back-calculated length-at-age data, with Von...

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Joy Plot of Length Frequencies

July 27, 2017
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Joy Plot of Length Frequencies

There has been a bit of a buzz recently about so-called “joyplots.” Wilke described joyplots as “partially overlapping line plots that create the impression of a mountain range.” I would describe them as partially overlapping densit...

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Age Bias Plot Changes in FSA

April 25, 2017
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Age Bias Plot Changes in FSA

In the last two weeks, I have posted twice about modifying age bias plots and Bland-Altman-like plots for comparing age estimates. From those posts, I have decided that I prefer to plot differences between the ages on the y-axis (as com...

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Bland-Altman Plot for Age Comparisons?

April 19, 2017
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Bland-Altman Plot for Age Comparisons?

Last week I posted about a modified age bias plot. In this post I began looking more deeply at an alternative plot called the Bland-Altman plot. Below, I describe this plot, demonstrate how to construct it in R, give a mild critique of its ...

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