趋向指标DMI计算及详解

的百分

比得到动向指数

dx

。由于

dx

的波动幅度 比较大，一般以一定的周期的平滑计算，得

到平均动向指标

adx

。具体过程如下：

dx=(didif Fisum) x 100

其中，

didif

为上升指标和下降指标的价差的绝对值

< br>

disum

为上升指标和下降指标的总和

adx

就是

dx

的一定周期

n

的移动平均值。

< br>

(5)

计算评估数值

adxr

在

指标中还可以添加

adxr

指标，以便更有利于行情的研判。

adxr

的计算公式为：

(

当日的

adx +

前一日的

adx) +2

和其他指标的计算一样，

由于选用的计算周期的不同，

dmi

指标也包括日

dmi

指标、周

dmi

指标、月

dm i

指标年

dmi

指标以及分钟

dmi

指标等各种类型。经常被用于股市研判的

是日

dmi

指

标和周

dmi

指标。虽然它们的计算时的取值有所不同，

另外，随着股市软件分析技术的发展，

但基本的计算方法一样。

投资者只需 掌握

dmi

形成的基本原理和计算方法，

dmi

指标去分析、研判股票行情。

无须去计算指标的数值，更为重要的是利用

Directional Movement Index (DMI)

Description

The Directional Movement Index (also known as DMI) is a momentum indicator that

was developed by J. Welles Wilder. It is calculated using the price, compares the

current price with the previous price range, and displays the result as an upward

movement line (+DI), and a downward movement line (-DI), between 0 and 100.

The DMI also calculates the strength of the upward or downward movement, and

displays the result as a trend strength line (ADX).

The DMI is displayed on its own chart, separate from the price bars, and is the

lower section in the chart shown above.

Calculation

Description: The DMI is the ratio of exponential moving averages of the greater of the

upward (U) and downward (D) price movements, and the true range (TR).

Calculation:

U = Hn - Hn-1 D = Ln-1 - Ln TR = (Hn - Ln) | (Hn - Cn-1) | (Cn-1 - Ln) EMAUP = EMAUn-1 + ((2 / (n

+

1))

*

(Un

-

EMAUn-1))

EMADOWN

=

EMADn-1

+

((2

/

(n

+

1))

*

(Dn

-

EMADn-1))

EMATR

=

EMATRn-1 + ((2 / (n + 1)) * (TRn - EMATRn-1)) +DI = EMAUP / EMATR -DI = EMADOWN / EMATR

DX = ABS(+DI - -DI) / (+DI + -DI)

ADX = EMADXn-1 + ((2 / (n + 1)) * (DXn - EMADXn-1))

Trading Use

The Directional Movement Index can be used in

both ranging and trending markets. In general, when the +DI line is above the -DI

line, the market is moving upwards, and when the -DI line is above the +DI line, the

market is moving downwards. The ADX line shows the strength of the move, and

the market is considered to be trending when the ADX line is above 30, and ranging

when the ADX line is below 30. There are several trading systems that use the DMI,

so there are several alternative uses of both the DI lines, and the ADX line.

(ranging and trending markets

Definition:

Day trading markets are referred to as either ranging or trending depending upon the

type of price movement that is currently occurring. The descriptions of these types of

markets are as follows :

Ranging

A ranging market is a market where the price is moving back and forth between a higher

price and a lower price. The higher price would be acting as resistance because it

prevents the price from moving above it, and the lower price would be acting as support

because it prevents the price from moving below it.

The price range of a ranging market can be small or large, and if the range is very small

the market would be considered to be in chop (moving sideways with very little upward or

downward movement).

Trending

A trending market is a market where the price is moving in a single direction, either up or

down, but not sideways.

There may be several small price reversals, but nothing large enough to prevent the

price movement from continuing in its original direction. A day trading trend may last for a

few minutes or a few hours, and longer term trends

may last for several weeks or

months.

)

DMI Points The Way To Profits

By Candy Schaap

A

A

A

|

The primary objective of the trend trader is to enter a trade in the direction of

the trend . Reading directional signals from price alone can be difficult and is

often misleading because price normally swings in both directions and changes

character between periods of low versus high volatility.

The directional movement indicator (also known as the directional movement

index - DMI) is a valuable tool for assessing price direction and strength. This

indicator was created in 1978 by J. Welles Wilder, who also created the popular

relative strength index . DMI tells you when to be long or short. It is especially

useful for trend trading strategies because it differentiates between strong and

weak trends, allowing the trader to enter only the strongest trends. DMI works

on all time frames and can be applied to any underlying vehicle (stocks, mutual

funds, exchange-traded funds , futures, commodities and currencies). Here,

we'll cover the DMI indicator in detail and show you what information it can

reveal to help you achieve better profits. (For background reading, see

Momentum And The Relative Strength Index

.)

DMI Characteristics

DMI is a moving average of range expansion over a given period (default 14).

The positive directional movement indicator (+DMI) measures how strongly

price moves upward; the negative directional movement indicator (-DMI)

measures how strongly price moves downward. The two lines reflect the

respective strength of the bulls versus the bears. Each DMI is represented by a

separate line (Figure 1). First, look to see which of the two DMI lines is on top.

Some short-term traders refer to this as the

dominant

DMI. The dominant DMI

is stronger and more likely to predict the direction of price. For the buyers and

sellers to change dominance, the lines must cross over.

A crossover occurs when the DMI on bottom crosses up through the dominant

DMI on top. Crossovers may seem like an obvious signal to go long/short, but

many short-term traders will wait for other indicators to confirm the entry or exit

signals to increase their chances of making a profitable trade. Crossovers of

the DMI lines are often unreliable because they frequently give false signals

when volatility is low and late signals when volatility is high. Think of crossovers

as the first indication of a

potential

change in direction. (For more insight, read

the

Moving Averages

tutorial.)

Source: TDAmeritrade Strategy Desk

Figure 1: The +DMI and -DMI are shown as separate lines. There are several false

crossovers ( Point 1) and one crossover at Point 2 that leads to an uptrend with

+DMI dominant. Note:The calculations for DMI are complicated and are referenced

elsewhere. Also, DMI is normally plotted in the same window with the ADX indicator,

which is not shown.

DMI is used to confirm price action (see Figure 2). The +DMI generally moves

in sync with price, which means that the +DMI rises when price rises, and it falls

when price falls. It is important to note that the -DMI behaves in the opposite

manner and moves counter-directional to price. The -DMI rises when price falls,

and it falls when price rises. This takes a little getting used to. Just remember

that the strength of a price move up or down is always recorded by a peak in

the respective DMI line.

Reading directional signals is easy. When the +DMI is dominant and rising,

price direction is up. When the -DMI is dominant and rising, price direction is

down. But the strength of price must also be considered. DMI strength ranges

from a low of 0 to a high of 100. The higher the DMI value, the stronger the

prices swing. DMI values over 25 mean price is directionally strong. DMI values

under 25 mean price is directionally weak.

Source: TDAmeritrade Strategy Desk

Figure 2: DMI is weak at Point 1 and price is choppy. The +DMI rises strongly above

25 at Point 2 and the uptrend follows. Note how +DMI moves with price at Point 3

and -DMI moves counter-directional to price at Point 4.

DMI Momentum

The great feature of DMI is the ability to see buying and selling pressure at the

same time, allowing the dominant force to be determined before entering a

trade. The strength of a swing high (bulls) is reflected in the +DMI peak, and the

strength of a swing low (bears) is seen in the -DMI peaks. The relative strength

of the DMI peaks tells the momentum of price and provides timely signals for

trading decisions. When the buyers are stronger than the sellers, the +DMI

peaks will be above 25 and the -DMI peaks will be below 25. This is seen in a

strong uptrend. But when the sellers are stronger than the buyers, the -DMI

peaks will be above 25 and the +DMI peaks will be below 25. In this case, the

trend will be down.

The ability of price to trend depends on continued strength in the dominant

DMI. A strong uptrend will show a series of rising +DMI peaks that remain

above the -DMI for extended periods of time (Figure 3). The opposite is true for

strong downtrends. When both DMI lines are below 25 and moving sideways,

there is no dominant force and trend trades are not appropriate. However, the

best trends begin after long periods where the DMI lines cross back and forth

under the 25 level. A low risk trade setup will occur after DMI expands above

the 25 level and price penetrates support/resistance.

Source: TDAmeritrade Strategy Desk

Figure 3: The +DMI crosses above 25 at Point 1 and remains above

the -DMI as the uptrend develops. Note the absence of any

crossover by -DMI during the uptrend. Here, the buyers are strong

(+DMI >25) and the sellers are weak (-DMI <25).

DMI Confirmation

DMI lines pivot, or change direction, when price changes direction. An

important concept of DMI pivots is they must correlate with structural pivots in

price. When price makes a pivot high, the +DMI will make a pivot high. When

price makes a pivot low, the -DMI will make a pivot high

(remember -DMI moves counter-directional to price).

The correlation between DMI pivots and price pivots is important for reading

price momentum. Many short-term traders watch for the price and the indicator

to move together in the same direction or times they diverge . One method of

confirming an asset's uptrend is to find scenarios when price makes a new pivot

high and the +DMI makes a new high. Conversely, a new pivot low combined

with a new high on the -DMI is used to confirm a downtrend. This is generally a

signal to trade in the direction of the trend or a trend breakout

Divergence, on the other hand is when the DMI and price

disagree

, or do not

confirm one another. An example is when price makes a new high, but the

+DMI makes a lower high. Divergence is generally a warning to manage risk

because it signals a change of swing strength and commonly precedes a

retracement or reversal. (For more on this topic, read

Divergences,

Momentum And Rate Of Change

.)

Source: TDAmeritrade Strategy Desk

Figure 4: This is an example of when the price and

indicator agree (Point 1), where price makes a new high

and +DMI makes a new high, signaling a long entry.

There is also an example of divergence (Point 2), where price makes a

new high and the +DMI makes a lower high; the result is a trend

retracement at Point 3.

DMI Contractions and Expansions

The DMI lines are a good reference for price volatility . Price goes through

repeated cycles of volatility in which a trend enters a period of consolidation

and then consolidation enters a period of trend. When price enters

consolidation, the volatility decreases. Buying pressure (demand) and selling

pressure (supply) are relatively equal, so the buyers and sellers generally agree

on the value of the asset. Once price has contracted into a narrow range, it will

expand as the buyers and sellers no longer agree on price. Supply and demand

is no longer in balance and consolidation changes to trend when price breaks

below support into a downtrend or above resistance into an uptrend. Volatility

increases as price searches for a new agreed value level.

Volatility cycles can be identified by comparing the slopes of the DMI lines that

move in opposite directions whenever range expansion or contraction occurs

(Figure 4). Many short-term traders will look for periods when the DMI lines

move away from one another and volatility increases. The farther the lines

separate, the stronger the volatility. Contractions occur when the