what is a var tree

Full Answer

What does var stand for?

Value at risk (VaR) is a statistic that measures and quantifies the level of financial risk within a firm, portfolio or position over a specific time frame. This metric is most commonly used by...

What is a Var of 2%?

For example, a financial firm may determine an asset has a 3% one-month VaR of 2%, representing a 3% chance of the asset declining in value by 2% during the one-month time frame. The conversion of the 3% chance of occurrence to a daily ratio places the odds of a 2% loss at one day per month.

How do you use VAR?

VaR. A final approach to VaR is to conduct a Monte Carlo simulation. This technique uses computational models to simulate projected returns over hundreds or thousands of possible iterations. Then, it takes the chances that a loss will occur, say 5% of the time, and reveals the impact.

What is a B-tree?

Introduction: B-Tree is a self-balancing search tree. In most of the other self-balancing search trees (like AVL and Red-Black Trees), it is assumed that everything is in main memory. To understand the use of B-Trees, we must think of the huge amount of data that cannot fit in main memory.

What type of trees are are in Newfoundland?

Tree Species of Newfoundland and LabradorAmerican Mountain Ash.Balsam Fir.Balsam Poplar.Black Ash.Black Spruce.Choke Cherry.Jack Pine.Mountain Alder.More items...

What is the most common tree in Alaska?

Alaska's forests are divided into two types: coastal and interior. Coastal forests are dominated by Western Hemlock (60%), Sitka Spruce (32%) and other softwoods (8%). Interior Alaska is vast with extensive stands dominated by White Spruce (64%), Birch (21%) and Poplars (15%).

What are species trees?

CoconutWeeping willowGinkgoNeem TreePapayaAmerican sycamoreTree/Representative species

What is a lodgepole pine tree?

Lodgepole pine is a highly adaptable tree that can grow in all sorts of environments, from water-logged bogs to dry sandy soils. Lodgepole pine is one of the first trees to invade after a wildfire. Its cones are protected by a seal of pitch that requires fire or heat to release the seeds.

What is the oldest tree in Alaska?

Some of the oldest Sitka Spruce are found to be 800 years old, over 12 feet in diameter, and 200 feet tall! These towering giants are a treasure of this ancient forest. The Tongass is the largest remaining coastal temperate rainforest in the world.

Which state has the most trees?

#1 Alaska. Alaska has a whopping 31.7 Million trees which not only makes it the state with the most trees, but with so few people living there compared to other states, it has 43,401 trees for every person living there.

What are the 3 types of trees?

Trees have been grouped in various ways, some of which more or less parallel their scientific classification: softwoods are conifers, and hardwoods are dicotyledons. Hardwoods are also known as broadleaf trees. The designations softwood, hardwood, and broadleaf, however, are often imprecise.

What's the oldest tree in the world?

Great Basin Bristlecone PineThe Great Basin Bristlecone Pine (Pinus longaeva) has been deemed the oldest tree in existence, reaching an age of over 5,000 years old. The bristlecone pine's success in living a long life can be attributed to the harsh conditions it lives in.

What was the first tree on earth?

ArchaeopterisThe first "tree" appears during the Devonian period, between 350 and 420 million years ago. This Progymnosperm is called Archaeopteris. Its wood resembles that of conifers, its trunk is thick, and it can reach up to 50 m. But it reproduces with spores, much like ferns.

Is Tamarack the same as lodgepole pine?

Murrayana is commonly known as the Lodgepole Pine, Sierra Lodgepole Pine, Sierra-Cascade Lodgepole Pine as well as Tamarack Pine. The currently accepted scientific name of Sierra lodgepole pine is Pinus contorta var. murrayana (Grev. & Balf.)

What does lodge pole pine look like?

A handsome native pine with yellowish green to dark green needles, twisted in bundles of two. It has a long, slender, pole-like trunk with a short, narrow, cone shaped crown. The flaky, thin bark is orange brown to grey or black.

Is lodgepole pine good for lumber?

The wood of Sierra lodgepole pine is straight grained, light, and uniform in texture, with small knots, making it suitable for lumber, plywood, and paneling. It is used for light framing materials, doors, windows, and furniture.

What is the most common pine tree in Alaska?

Sitka spruce (Picea sitchensis) is common in Alaska, especially southeast Alaska. Although it is in the pine family, it is a spruce species. Sitka spruces are large, up to 230 feet tall and 6 feet in diameter.

What is the state tree of Alaska?

Sitka spruceAlaska / State treePicea sitchensis, the Sitka spruce, is a large, coniferous, evergreen tree growing to almost 100 meters tall, with a trunk diameter at breast height that can exceed 5 m. It is by far the largest species of spruce and the fifth-largest conifer in the world, and the third-tallest conifer species. Wikipedia

What trees can grow in Alaska?

Alaska-grown apple trees usu- ally have super-hardy crabapples such as Malus baccata, the Siberian crabapple; or varieties such as Columbia, Dolgo, Ranetka or Red Splendor as rootstocks. The apple varieties Antanovka and Beautiful Arcade are also used and have generally proved satisfactory as rootstocks.

What are the largest trees in Alaska?

Sitka Spruce (Alaska's State Tree) The Sitka Spruce (Picea sitchensis) is a large evergreen tree growing to 120-180 feet tall, and with a trunk diameter of 3-5 feet. It is by far the largest species of spruce, and the third tallest tree species in the world (after Coast Redwood and Coast Douglas-fir).

What is the outer covering of a tree trunk?

If you could tunnel into a woody plant's stem, whether the trunk of a tree or a twig on a shrub, you would first encounter bark , then cambium, and finally wood or xylem. Bark is the outer covering on the trunk, twigs, and woody roots. The outer bark we are familiar with is a layer of dead corky cells protecting the rest of the stem.

How tall is a tree?

Though no scientific definition exists to separate trees and shrubs, a useful definition for a tree is a woody plant having one erect perennial stem (trunk) at least three inches in diameter at a point 4-1/2 feet above the ground, a definitely formed crown of foliage, and a mature height of at least 13 feet. This definition works fine, though some ...

What are some plants that are closely related to a tree?

Some are closely related, like ponderosa pine and limber pine. Others are not closely related at all, like eastern redcedar and silver maple. However, trees, shrubs, and vines all have one thing that separates them from the rest of the plant world: a woody stem that is perennial or that lives for many years. Grasses and certain other plants may be ...

What is a deciduous tree?

Trees, shrubs, and woody vines can be classified as deciduous or evergreen. If a plant's leaves stay green and alive through the winter it is called an evergreen. Examples found in Utah are pines, spruces, and junipers. Plants whose leaves die in autumn and fall off, such as elms, maples, and ashes, are called deciduous.

How tall is a woody vine?

It will usually have a height less than 13 feet and stems no more than about three inches in diameter. Woody vines are plants that have perennial stems that cannot support themselves. Vines use other plants or objects to rise above the ground or they lie along the ground.

What is the inner bark of a plant?

The inner bark, or phloem, is a live spongy layer just inside the outer bark that moves sugars and other substances from the leaves to the stem, roots, and other places where they are needed. Inner bark eventually grows out to form part of the outer bark. New bark is constantly being made on the inside and pushed out.

What is the wood that dies one ring at a time called?

This wood dies one ring at a time and becomes heartwood. Heartwood often is filled with dark colored substances that help it resist decay, as in redcedar's red to purple heartwood. The active living wood on the outside of the stem, one to many rings wide, is called the sapwood.

How tall is a chokecherry tree?

Chokecherry is a suckering shrub or small tree growing to 1–6 m (3 ft 3 in–19 ft 8 in) tall, rarely to 10 m (32 ft 10 in). The leaves are oval, 2.5–10 cm (1–4 in) long and 1.2–5 cm ( 1⁄2 –2 in) wide, with a serrated margin. The stems rarely exceed 2 cm ( 3⁄4 in) in length.

Where does Prunus virginiana grow?

Prunus virginiana, commonly called bitter-berry, chokecherry, Virginia bird cherry, and western chokecherry (also black chokecherry for P. virginiana var. demissa ), is a species of bird cherry ( Prunus subgenus Padus) native to North America. The natural historic range of P. virginiana includes most of Canada (including Northwest Territories, but excluding Yukon, Nunavut, and Labrador), most of the United States (including Alaska, but excluding some states in the Southeast ), and northern Mexico ( Sonora, Chihuahua, Baja California, Durango, Zacatecas, Coahuila, and Nuevo León ).

What is the purpose of chokecherry leaves?

The leaves of the chokecherry serve as food for caterpillars of various Lepidoptera. In 2007, Governor John Hoeven signed a bill naming the chokecherry the official fruit of the state of North Dakota, in part because its remains have been found at more archeological sites in the Dakotas than anywhere else.

How big are drupes?

They are 8–13 mm (0.31–0.51 in) across. The fruits ( drupes) are about 6–14 mm (0.24–0.55 in) in diameter, range in color from bright red to black, and possess a very astringent taste, being both somewhat sour and somewhat bitter. They get darker and marginally sweeter as they ripen.

Is chokecherry a pest?

The wild chokecherry is often considered a pest, as it is a host for the tent caterpillar, a threat to other fruit plants. Other, more appreciated cultivars of the chokecherry are known. 'Canada Red' and 'Schubert' have leaves that mature to purple and turn orange and red in the autumn.

What is a vtree?

vtree is designed to be quick and easy to use, so that it is convenient for data exploration, but also flexible enough that it can be used to prepare publication-ready figures. To generate a basic variable tree, it is only necessary to specify a data frame and some variable names.

What is a tree with two variables?

A tree with two variables is similar to a two-way contingency table. In the example above, Sexis shown within levels of Severity. This corresponds to the following contingency table, where the percentages within each column add to 100%. These are called column percentages.

What color is severity in vtree?

Also by default, vtreeautomatically assigns a color palette to the nodes of each variable. Severityhas been assigned red hues (lightest for Mild, darkest for Severe), while Sexhas been assigned blue hues (light blue for females, dark blue for males). The node representing missing values of Severityis colored white to draw attention to it.

What is the root node of a variable tree?

The root node of the variable tree represents the entire data frame. The root node has a child for each observed value of the first variable that was specified. Each of these child nodes represents a subset of the data frame with a specific value of the variable, and is labeled with the number of observations in the subset and the corresponding percentage of the number of observations in the entire data frame. The nthlayer below the root of the variable tree corresponds to the nthvariable specified. Apart from the root node, each node in the variable tree represents the subset of its parent defined by a specific observed value of the variable at that layer of the tree, and is labeled with the number of observations in that subset and the corresponding percentage of the number of observations in its parent node.

How many patients are in a variable tree?

A variable tree consists of nodesconnected by arrows. At the top of the diagram above, the rootnode of the tree contains all 46 patients. The rest of the nodes are arranged in successive layers, where each layer corresponds to a specific variable. Note that this highlights one difference between variable trees and some other kinds of trees: each layer of a variable tree corresponds to just one variable. (In a decision tree, by contrast, different branches can have different sequences of variable splits.)

Why do we need variable trees?

In many cases, you may wish to generate several different variable trees to investigate a collection of variables in a data frame. For example, it is often useful to change the order of variables, prune parts of the tree, etc.

Why was vtree developed?

And although the errors that make it into published articles are often minor, they can sometimes be disastrous. One motivation for developing vtree was to make flow diagrams reproducible. The ability to reproducibly generate variable trees also means that when a data set is updated, a revised tree can be automatically produced.

Tree Model

Tree models are collection of the “if-then-else” rules to describe the data. Tree models, also called Classification and Regression Trees ( CART ),3 decision trees, or just trees, are an effective and popular classification (and regression) method initially developed by Leo Breiman and others in 1984 [1].

Using only Two Predictors

For visualisation purpose, we aim at using only two predictors, Age and Fare to predict the survived passengers. We start by loading the data. The data looks like as:

Ensemble Learning

When it comes to prediction, however, harnessing the results from multiple trees is typically more powerful than using just a single tree. In particular, the random forest and boosted tree algorithms almost always provide superior predictive accuracy and performance. There are two main variants of ensemble models: bagging and boosting.

Variable Importance

Tree models can be used to determine which predictors plays a critical role in predicting the outcome. There are two ways to measure variable importance [1]:

What are the invaders of the Metrosideros polymorpha forests?

In the wet forests these include the strawberry guava ( Psidium littorale ), albizia ( Falcataria moluccana ), and "purple plague" ( Miconia calvescens ). In drier areas, problematic invaders include faya tree ( Myrica faya) and Christmasberry ( Schinus terebinthifolius ). Alien grasses such as meadow ricegrass ( Ehrharta stipoides) may form an understory that prevents or inhibits natural regeneration of the forests. In drier areas, M. polymorpha has to compete with silk oak ( Grevillea robusta) and fountain grass ( Pennisetum setaceum ).

What is the Hawaiian tree?

Many native Hawaiian traditions refer to the tree and the forests it forms as sacred to Pele, the volcano goddess, and to Laka, the goddess of hula. ʻŌhiʻa trees grow easily on lava, and are usually the first plants to grow on new lava flows.

What is the name of the fungus that attacks the hia forests?

Metrosideros polymorpha flowering Alaka'i swamp in Kaua'i. More recently, a strain of fungus initially identified as Ceratocystis fimbriata has attacked the ʻōhiʻa forests of the Big Island, causing Rapid 'Ōhi'a Death. The disease gets this name because healthy trees appear to die within a few days to a few weeks.

Where is the Metrosideros polymorpha native to?

Metrosideros polymorpha was originally classified as a variety of M. collina, native to Rarotonga, Tahiti, and other islands of Polynesia, but now is generally accepted as a distinct Hawaiian endemic species.

Where do Metrosideros grow?

It grows from sea level right up to the tree line at elevations of 2,500 m (8,200 ft) and is commonly found in moist and dry forests, high shrublands, and is a colonizer of recent lava flows. It is relatively slow growing. Dominant in cloud forests above 400 m (1,300 ft), the tree is also common in seasonally wet forests, where it may be dominant or form mixtures with the native Acacia koa .

How tall is a sage tree?

It is a highly variable tree, being 20–25 m (66–82 ft) tall in favorable situations, and a much smaller prostrate shrub when growing in boggy soils or directly on basalt. It produces a brilliant display of flowers, made up of a mass of stamens, which can range from fiery red to yellow.

Is a lehua a tree?

It is a common misconception that the word ʻōhiʻa is used to refer to the tree and that the word lehua refers only to its flowers. The Hawaiian Dictionary (Pukui and Elbert 1986: 199) defines lehua with these words: "The flower of the ʻōhiʻa tree... also the tree itself [emphasis added]." Thus the Metrosideros polymorpha may be referred to correctly as a lehua tree, or as an ʻōhiʻa lehua, or simply an ʻōhiʻa.

What is a B tree?

B-Tree is a self-balancing search tree. In most of the other self-balancing search trees (like AVL and Red-Black Trees), it is assumed that everything is in main memory. To understand the use of B-Trees, we must think of the huge amount of data that cannot fit in main memory. When the number of keys is high, the data is read from disk in ...

Why use B tree?

The main idea of using B-Trees is to reduce the number of disk accesses. Most of the tree operations (search, insert, delete, max, min, ..etc ) require O (h) disk accesses where h is the height of the tree. B-tree is a fat tree.

Where does the insert of a node in a B tree occur?

Insertion of a Node in B-Tree happens only at Leaf Node.

Is all leaves at the same level?

All leaves are at the same level.

Overview

Description

Taxonomy

Distribution

Ecology

Cultivation

Toxicity

Uses