Distance-based ordination
16 important questions on Distance-based ordination
What are multivariate analyses (MVA's)?
- ecological phenomena are inherently complex
- often with many response variables
Why would you not do seperate univariates analyses?
- Many independent tests: not efficient
- Multiple testing: loose statistical power
- Multicollinearity: several species may response similarly to predictors (redundancy)
What are the 3 types of ordination plots?
- Scatterplot (sites)
- Biplot (sites + species)
- Triplot (sites + species + predictors)
- Higher grades + faster learning
- Never study anything twice
- 100% sure, 100% understanding
For my 1st exam I got a C. Then, I started looking for ways to learn better and I came across Study Smart. Since then I have scored a A+, A, A- and another A. I highly recommend it to everyone who wants to hear it. I am so happy with it!!
I was struggling to finish all my first-year subjects for 3 years. Then I discovered Study Smart, which helped me to finish all of them within 3 months.
Because of StudySmart, things are going well in many ways. Before, I always had study stress and no time for anything. Now I feel calm and confident (because of the program). I used to score a B, now I usually score an A or A+.
Hey Chris, I really want to thank you very much for developing the platform, I usually got around C for my exams, now I scored an A+, an A and a A- !!
Since using Study Smart, my average has increased significantly. I even completed a statistics course with a A+ while I'm bad at statistics. I took on extra courses this year, because of Study Smart. Thanks so much!
Ever since I started studying with StudySmart I passed all my exams !!! No more re-sits!! At first, I was happy with a pass and now I only get good grades. Many thanks!
I aced all the courses I studied with Study Smart. For law, I first scored a D, and now an A! I’m 100% sure that I’ll pass all the courses I study with Study Smart.
I always thought I studied well. My grades were fine. I could never have imagined that applying these study skills would have such a huge and direct impact on my grades, my speed and the pleasure I have in learning.
For the first time, I finally feel totally confident about the way I learn. I have the perfect overview and make great progress in terms of speed and the grades I get. Thanks, Chris!
I immediately started to enjoy learning again, and my grades soared. All of a sudden, everything went better. I highly recommend Study Smart to all students..
Being able to create my materials online made the process of studying so much smoother and quicker. I no longer have to spend a huge amount of my time on creating my summaries.
At first, my notes were a mess. Now I use Study Smart to take my notes in a perfectly structured way. It helps me to save a lot of time and do other things I enjoy.
Students that study with Study Smart get better grades. The system applies all the learning methods in such a way that both well-performing students and students who struggle perform much better.
Hi Chris, I would like to thank you very much. Last year I scored C on a course, and this year I got an A+ thanks to your method! Thank you very much!
The largest effect is that my child is more enthusiastic about school! Every parent wants their children to be happy at school, Study Smart made it happen.
In high school, I failed several exams, and that has really changed now. I actually needed this tool very much back then. Since I started studying with StudySmart, I haven't had any D's. My average score is now an A and those are results I would have never had in the past
With my old method, I passed only 3 out of 8 courses. Since I started taking my notes digitally in Study Smart, I have passed all my courses on the first try. For me, StudySmart takes away the stress of wondering if I will pass or not.
Thanks to StudySmart, I passed all my exams, and with better grades than before! On top of that, I have mastered a very good study method now, which I am confident will help me earn my degree.
How are euclidean distances calculated?
What are the steps of polar ordination: axis 2?
- Calculate distance between sites in terms of species composition
- Select the two most different sites: these are placed on opposite ends (poles) of axis 1
- Order the remaining sites between these poles
- Choose sites for axis 2 perpendicular to axis 1: select 2 other sites which are close together on axis 1, but very dissimilar
- Order all sites between these poles on axis 2
What is an ordination diagram?
What is a short gradient?
What is the abundace paradox?
Two locations sharing all species could appear more different (thus higher distance) than two locations which do not share any species but which have low abundances!
What are the solutions for double zeros?
- log(1+x) (reducing the influence of large values)
- sqrt(x) (reducing the influence of large values)
- ‘Hellinger’ (computing sqrt of relative abundances per location)
And/or use an asymmetric distance measure
- measures that treat double zeros and double presences asymmetrically
What is Hellinger distance?
- less senstive to abundance paradox and double-zero problem
What are the disadvantages of Polar ordination?
- Heuristic rules rather than a formal model
- Axes are not statistically independent by design
- Different people will end up with different ordinations
What is the Principal Coordinates Analysis (PCoA)?
- Based on robust mathematics
- Axes are statistically independent by design
- The same solution every time (on the same dataset)
What is the aim of nonmetric multidimensional scaling?
Why can/will multiple people performing polar ordination on the same dataset arrive at different ordinations, especially if the dataset becomes larger and more complex?
What can the Manhattan distance on presence-absence data be interpreted as?
What are Hellinger distances?
The question on the page originate from the summary of the following study material:
- A unique study and practice tool
- Never study anything twice again
- Get the grades you hope for
- 100% sure, 100% understanding
