強力指數指標是由Alexander Elder 博士根據價格波動以及交易量開發而來，簡稱FI。它可以衡量市場中多頭和空頭的力量。該指標結合2日或者13日指數移動平均線（EMA）使用時會給出較好的交易信號。
• 2日EMA可以跟蹤短期的買賣雙方力量。
• 13日EMA被用來測量中期的口頭和多頭力量。
如果該指標大於零，則說明是買方市場，小於零則為賣方市場。如果該指標圍繞在零軸週圍波動，說明市場處於調整期，不在任何一方掌控之中。
• FI為正數時，它的值越大說明牛市力量越強。
• FI為負數時，它的值越小說明空頭力量越大。
• 如果FI的絕對值小，說明交易量在下降或者大的交易量沒有成功的推動價格上升。這兩個原因都有可能帶來反轉。
2日FI被用作Eder 的三重濾網交易系統的一部分。
交易信號
始終要跟隨趨勢交易——可以根據13日EMA的斜率判斷出。
• 如果出現看漲背離且FI值為負數時，做多。
• 如果出現看跌背離且FI為正數時，做空。
完整的交易策略可以在Alexander Elder 的《以交易為生》一書中找到。
示例：
澳大利亞綜合股以及 13日EMA和 FI。
1. FI的快速下降預示著下降趨勢的結束，同時它也發出關於價格試探前期低點的警告。
2. [L] 處看漲背離做多，同時等待EMA向上傾斜。
3. FI不斷下降的高點預示著上漲動力正在逐漸減弱。此時，出現看跌背離，但不應該下單——EMA仍然呈上升趨勢。
4. FI跌破零軸，說明買方喪失了控制力。[S] 處當EMA向下傾斜時做空。
計算公式
FI指標的計算方法是，當日的收盤價減去昨日的收盤價，然後再乘以交易量：
FI = (今日收盤價 – 昨日收盤價) * 交易量
Force Index
Developed by Dr Alexander Elder, the Force index combines price movements and volume to measure the strength of bulls and bears in the market. The raw index is rather erratic and better results are achieved by smoothing with a 2-day or 13-day exponential moving average (EMA).
• The 2-day EMA of Force is used to track the strength of buyers and sellers in the short term;
• The 13-day EMA of Force measures the strength of bulls and bears in intermediate cycles.
If the Force index is above zero it signals that the bulls are in control. Negative Force index signals that the bears are in control. If the index whipsaws around zero it signals that neither side has control and no strong trend exists.
• The higher the positive reading on the Force index, the stronger is the bulls' power.
• Deep negative values signal that the bears are very strong.
• If Force index flattens out it indicates that either (a) volumes are falling or (b) large volumes have failed to significantly move prices. Both are likely to precede a reversal.
The 2-day Force index is used as part of Dr Eder's Triple Screen trading system.
Trading Signals
Only trade in the direction of the trend - indicated by the slope of the 13-day EMA.
• Go long if the Force index is below zero and there is a bullish divergence.
• Go short if the Force index is above zero and there is a bearish divergence.
Complete trading rules for the Force index can be found in Trading For A Living by Dr Alexander Elder.
EXAMPLE
The All Ordinaries Index (Australia) is shown with 13-day exponential moving average (EMA) and Force Index.
1. A deep spike marks the end of a down-trend but it also warns traders to expect a re-test of the previous bottom.
2. Go long [L] on the bullish divergence. Wait for the EMA to turn upwards.
3. Declining peaks signal that bulls' strength is fading. No action is taken on the bearish divergence - the EMA is still rising.
4. The Force index falling below zero indicates that the bulls have lost control. On the strength of the bearish divergence - go short [S] when the EMA turns downward.
Setup
See Indicator Panel for directions on how to set up an indicator. The default settings for the Force index are :
• 13-day exponential moving average.
Formula
The Force index is calculated by subtracting yesterday's close from today's close, before multiplying by volume:
Force index = (Close [today] - Close [yesterday]) * Volume
本文翻譯由兄弟財經提供
文章來源：http://www.incrediblecharts.com/indicators/force_index.php