Stock Price Trends
Stock price trends estimated using linear regression.
Summary
Key facts
- The primary trend is decreasing.
- The decline rate of the primary trend is 45.10% per annum.
- ISRG price at the close of September 18, 2026 was $393.33 and was higher than the top border of the primary price channel by $8.82 (2.29%). This indicates a possible reversal in the primary trend direction.
- The secondary trend is increasing.
- The growth rate of the secondary trend is 45.91% per annum.
- ISRG price at the close of September 18, 2026 was inside the secondary price channel.
- The direction of the secondary trend is opposite to the direction of the primary trend. This indicates a possible reversal in the direction of the primary trend.
Linear Regression Model
Model equation:
Yi = α + β × Xi + εi
Top border of price channel:
Exp(Yi) = Exp(a + b × Xi + 2 × s)
Bottom border of price channel:
Exp(Yi) = Exp(a + b × Xi – 2 × s)
where:
i - observation number
Yi - natural logarithm of ISRG price
Xi - time index, 1 day interval
σ - standard deviation of εi
a - estimator of α
b - estimator of β
s - estimator of σ
Exp() - calculates the exponent of e
Primary Trend
Start date: November 7, 2025
End date: September 15, 2026
a = 8.8658
b = -0.0016
s = 0.0415
Annual growth rate:
Exp(365 × b) – 1
= Exp(365 × -0.0016) – 1
= -45.10%
Price channel spread:
Exp(4 × s) – 1
= Exp(4 × 0.0415) – 1
= 18.04%
November 7, 2025 calculations
Top border of price channel:
Exp(Y1,039)
= Exp(a + b × X1,039 + 2 × s)
= Exp(a + b × 1,509 + 2 × s)
= Exp(8.8658 + -0.0016 × 1,509 + 2 × 0.0415)
= Exp(6.4695)
= $645.16
Bottom border of price channel:
Exp(Y1,039)
= Exp(a + b × X1,039 – 2 × s)
= Exp(a + b × 1,509 – 2 × s)
= Exp(8.8658 + -0.0016 × 1,509 – 2 × 0.0415)
= Exp(6.3037)
= $546.58
September 15, 2026 calculations
Top border of price channel:
Exp(Y1,251)
= Exp(a + b × X1,251 + 2 × s)
= Exp(a + b × 1,821 + 2 × s)
= Exp(8.8658 + -0.0016 × 1,821 + 2 × 0.0415)
= Exp(5.9569)
= $386.41
Bottom border of price channel:
Exp(Y1,251)
= Exp(a + b × X1,251 – 2 × s)
= Exp(a + b × 1,821 – 2 × s)
= Exp(8.8658 + -0.0016 × 1,821 – 2 × 0.0415)
= Exp(5.7911)
= $327.37
Description
- The primary trend is decreasing.
- The decline rate of the primary trend is 45.10% per annum.
- ISRG price at the close of September 18, 2026 was $393.33 and was higher than the top border of the primary price channel by $8.82 (2.29%). This indicates a possible reversal in the primary trend direction.
Secondary Trend
Start date: July 17, 2026
End date: September 18, 2026
a = 4.0590
b = 0.0010
s = 0.0439
Annual growth rate:
Exp(365 × b) – 1
= Exp(365 × 0.0010) – 1
= 45.91%
Price channel spread:
Exp(4 × s) – 1
= Exp(4 × 0.0439) – 1
= 19.17%
July 17, 2026 calculations
Top border of price channel:
Exp(Y1,210)
= Exp(a + b × X1,210 + 2 × s)
= Exp(a + b × 1,761 + 2 × s)
= Exp(4.0590 + 0.0010 × 1,761 + 2 × 0.0439)
= Exp(5.9695)
= $391.32
Bottom border of price channel:
Exp(Y1,210)
= Exp(a + b × X1,210 – 2 × s)
= Exp(a + b × 1,761 – 2 × s)
= Exp(4.0590 + 0.0010 × 1,761 – 2 × 0.0439)
= Exp(5.7941)
= $328.36
September 18, 2026 calculations
Top border of price channel:
Exp(Y1,254)
= Exp(a + b × X1,254 + 2 × s)
= Exp(a + b × 1,824 + 2 × s)
= Exp(4.0590 + 0.0010 × 1,824 + 2 × 0.0439)
= Exp(6.0347)
= $417.69
Bottom border of price channel:
Exp(Y1,254)
= Exp(a + b × X1,254 – 2 × s)
= Exp(a + b × 1,824 – 2 × s)
= Exp(4.0590 + 0.0010 × 1,824 – 2 × 0.0439)
= Exp(5.8593)
= $350.49
Description
- The secondary trend is increasing.
- The growth rate of the secondary trend is 45.91% per annum.
- ISRG price at the close of September 18, 2026 was inside the secondary price channel.