Thursday, 4 February 2021

Constructing a Pleasant Little Solar-Heated Outdoor Reading Nook

Constructing a Pleasant Little Solar-Heated Outdoor Reading Nook

With Covid-19 lockdowns and the possibility that vitimin D is helpful in preventing the condition, I decided to build a nice little solar-heated outdoor reading nook.  My deck faces south, so at noon there is a good deal of mid-winter sunshine, even at the high latitude where I live (about 54 degrees north).


 

It was pretty easy to build, even for someone who isn’t much of a carpenter:

  • I bought some light panel boards.  I bought 3 panels, 2 feet by 4 feet, thickness of about a quarter inch.
  • Since they are kind of flimsy, I reinforced them along the edges, with 1 by 2 studs, using ¾ inch number 8 wood screws.  I used these size screws throughout the project.
  • Then, to add some extra strength at the corners, I added metal L-shaped brackets for bracing.
  • I wrapped one side of the panels (the one without the 1 by 2 showing) with mylar, using packing tape to fix the mylar to the panels.
  • To make a 3 piece unit that could be folded up (kind of like a triptych with the sun as my artwork), I put hinges in.  I had to be careful to use different sizes of hinges to ensure that the unit could fold up nicely.
  •  Note also that you have to have the mylar surfaces arranged in such a way that they all reflect the sunlight centrally, once the unit is unfolded.
     

  •  


I set the unit up with the mylar surface facing the sun at around local noon (solar time).  The left and right panels were put at about a 45 degree angle to the center panel, with the mylar surfaces facing the sun.  The unit stood up by itself nicely, though in an unsheltered spot the wind would probably be a problem.  One could add a bottom platform (a sort of stand) to take care of this.



On a day that was about at the freezing point, the area where I placed my chair was about 10 degrees Celius or 15 degrees Farenheit warmer than the ambient air.  While wearing a padded vest over my shirt, I could even roll up my shirt sleeves and dispense with headwear and gloves.


This also provides plenty of sunlight for reading, which is handy when using a kindle.  If you are using your phone or ipad, there can be some glare, though it is managable if you orient the screen the right way.  I found that I could comfortably sit and read for at least a couple of hours, especially after high noon.  Plus, I got a fair bit of sunshine and fresh air, which is good for the spirit.


Once I was done reading, I folded up the unit and stored it against the wall of the house, putting a home-made planter in front of it (weighted down with a few bricks), so that it wouldn’t fall or be blown down in the wind.

One warning – after finishing the project you can almost guarantee a spell of cloudy weather.  :)

Come spring, I plan to use this unit to jump-start our bedding plants.  In the summer, it would likely be too hot to use for much, except maybe keeping a coffee pot warm.  I will have to try that.

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And, here’s a pleasant little travel story about a place where a solar-heated reading nook could be quite useful.  You would definitely have to be careful about your unit being knocked over by the wind, though.

A Drive Across Newfoundland

 


U.S.: https://www.amazon.com/dp/B07NMR9WM8

U.K.:  https://www.amazon.co.uk/dp/B07NMR9WM8

Germany: https://www.amazon.de/dp/B07NMR9WM8

Japan: https://www.amazon.co.jp/dp/B07NMR9WM8

Canada: https://www.amazon.ca/dp/B07NMR9WM8

Australia: https://www.amazon.com.au/dp/B07NMR9WM8

India: https://www.amazon.in/dp/B07NMR9WM8

Newfoundland, Canada’s most easterly province, is a region that is both fascinating in its unique culture and amazing in its vistas of stark beauty. The weather is often wild, with coastal regions known for steep cliffs and crashing waves (though tranquil beaches exist too). The inland areas are primarily Precambrian shield, dominated by forests, rivers, rock formations, and abundant wildlife. The province also features some of the Earth’s most remarkable geology, notably The Tablelands, where the mantle rocks of the Earth’s interior have been exposed at the surface, permitting one to explore an almost alien landscape, an opportunity available on only a few scattered regions of the planet.

The city of St. John’s is one of Canada’s most unique urban areas, with a population that maintains many old traditions and cultural aspects of the British Isles. That’s true of the rest of the province, as well, where the people are friendly and inclined to chat amiably with visitors. Plus, they talk with amusing accents and party hard, so what’s not to like?

This account focusses on a two-week road trip in October 2007, from St. John’s in the southeast, to L’Anse aux Meadows in the far northwest, the only known Viking settlement in North America. It also features a day hike visit to The Tablelands, a remarkable and majestic geological feature. Even those who don’t normally consider themselves very interested in geology will find themselves awe-struck by these other-worldly landscapes.

Monday, 25 January 2021

How do you choose the best linear regression model?

How do you choose the best linear regression model?

There are a number of methods and considerations for choosing the “best” regression method, regardless of the software and/or R package you are using. The guidelines below are relevant to R, Python, SPSS or whatever.

Some packages are easier than others to use (e.g. economists prefer Stata, social scientists tend to prefer SPSS, lots of people like open source products like R or Python) but they all do much the same thing, in terms of the math. Similarly, R has regression routines in the base package, but there are also lots of specialized packages that have been optimized to make life easier (assuming that the package will load).

Picking the “best” model is really up to the analyst, regardless of the package that is used.

·        What are you predicting? If it is a continuous variable (within some range), then you want to use some form of multiple regression. If it is a probability of some event occurring (e.g. will a student graduate) then you want to use some form of logistic regression. There are also more specialized routines (e.g. hierarchical regression), used for particular purposes.

·        Consider the theory behind your regression model, while choosing dependent variables. This might be derived from previous published research, subject matter experts, or just common sense.

·        You may want to use indicator variables (“dummy variables”) as well as numeric variables. That would be for non-numeric variables such as gender.

·        Different variables can be tested, based on theoretical considerations or exploratory data analysis. Examining scatter plots of the possible independent variables against the dependent can help. Also look at your variables, as to whether they fit the assumptions of regression analysis.

·        The above analysis might lead you to performing data transformations that are needed to linearize some variables (e.g. you might have to test a quadratic) or to ensure that you aren’t violating any assumptions (e.g. a log transform if the data is skewed). Some R packages might do these transformations if you request them, other times you might have to do them in a data step.

·        Once you have settled on a reasonable set of variables, test your model. You will usually be interested in the (adjusted) R-square of the model, and how that changes depending on which variables are in the model. The better the model, the higher the model R-square (i.e. the data fits the model better). You can also use an F-test to see if adding a variable is justified.

·        There are a number of standard model building methods, such as forward selection, backward selection or stepwise selection. They all have their advantages and disadvantages (and may go in and out of fashion over time).

·        You also have to look out for multi-collinearity, where two or more independent variables are themselves correlated. There are diagnostics for this (e.g. VIF) as well as indications that point to multi-collinearity (e.g. a variable has a counter-intuitive positive or negative sign).

·        Consider interaction effects, where the effect of a variable on a regression depends on another variable. Keep in mind that models with a lot of interactions (especially 3-way or more) are difficult to interpret and explain to others.

·        Examine outliers to see if there are some that are having an inordinate effect on the regression. There are diagnostics such as DFITS and DFBETAs for that.

·        It can be interesting to compare traditional statistical modelling to newer data science techniques. You would expect them to come to similar conclusions, though the “black box” nature of many machine learning techniques can make the comparisons difficult to do.

·        Try not to take criticism of your model personally. There are so many possibilities for a complex model, that there is bound to be disagreement.

·        And always remember the phrase “All models are wrong, but some are useful” (usually attributed to G. Box).


 

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Here's something else to read, if you are so inclined.  All work and no play, makes one a dull person, or so they say.

A Drive Across Newfoundland

 


U.S.: https://www.amazon.com/dp/B07NMR9WM8

U.K.:  https://www.amazon.co.uk/dp/B07NMR9WM8

Germany: https://www.amazon.de/dp/B07NMR9WM8

Japan: https://www.amazon.co.jp/dp/B07NMR9WM8

Canada: https://www.amazon.ca/dp/B07NMR9WM8

Australia: https://www.amazon.com.au/dp/B07NMR9WM8

India: https://www.amazon.in/dp/B07NMR9WM8

Newfoundland, Canada’s most easterly province, is a region that is both fascinating in its unique culture and amazing in its vistas of stark beauty. The weather is often wild, with coastal regions known for steep cliffs and crashing waves (though tranquil beaches exist too). The inland areas are primarily Precambrian shield, dominated by forests, rivers, rock formations, and abundant wildlife. The province also features some of the Earth’s most remarkable geology, notably The Tablelands, where the mantle rocks of the Earth’s interior have been exposed at the surface, permitting one to explore an almost alien landscape, an opportunity available on only a few scattered regions of the planet.

The city of St. John’s is one of Canada’s most unique urban areas, with a population that maintains many old traditions and cultural aspects of the British Isles. That’s true of the rest of the province, as well, where the people are friendly and inclined to chat amiably with visitors. Plus, they talk with amusing accents and party hard, so what’s not to like?

This account focusses on a two-week road trip in October 2007, from St. John’s in the southeast, to L’Anse aux Meadows in the far northwest, the only known Viking settlement in North America. It also features a day hike visit to The Tablelands, a remarkable and majestic geological feature. Even those who don’t normally consider themselves very interested in geology will find themselves awe-struck by these other-worldly landscapes.

A Ride on the Kettle Valley Rail Trail: A Biking Journal Kindle Edition

by Dale Olausen (Author), Helena Puumala (Editor)


The Kettle Valley Rail Trail is one of the longest and most scenic biking and hiking trails in Canada. It covers a good stretch of the south-central interior of British Columbia, about 600 kilometers of scenic countryside. British Columbia is one of the most beautiful areas of Canada, which is itself a beautiful country, ideal for those who appreciate natural splendour and achievable adventure in the great outdoors.

The trail passes through a great variety of geographical and geological regions, from mountains to valleys, along scenic lakes and rivers, to dry near-desert condition grasslands. It often features towering canyons, spanned by a combination of high trestle bridges and long tunnels, as it passes through wild, unpopulated country. At other times, it remains quite low, in populated valleys, alongside spectacular water features such as beautiful Lake Okanagan, an area that is home to hundreds of vineyards, as well as other civilized comforts.

The trail is a nice test of one’s physical fitness, as well as one’s wits and adaptability, as much of it does travel through true wilderness. The views are spectacular, the wildlife is plentiful and the people are friendly. What more could one ask for?

What follows is a journal of two summers of adventure, biking most of the trail in the late 1990s. It is about 33,000 words in length (2 to 3 hours reading), and contains numerous photographs of the trail. There are also sections containing a brief history of the trail, geology, flora and fauna, and associated information.

After reading this account, you should have a good sense of whether the trail is right for you. If you do decide to ride the trail, it will be an experience you will never forget.

Amazon U.S.: https://www.amazon.com/dp/B01GBG8JE0

Amazon U.K.: https://www.amazon.co.uk/dp/B01GBG8JE0

Amazon Germany: https://www.amazon.de/dp/B01GBG8JE0

Amazon Canada: https://www.amazon.ca/dp/B01GBG8JE0

Amazon Australia: https://www.amazon.com.au/dp/B01GBG8JE0