Contents

# Đường xu hướng

Trend lines can be added to all 2D chart types except for Pie and Stock charts.

Để truy cập lệnh này...

Choose Insert - Trend Line (Charts)

If you insert a trend line to a chart type that uses categories, like Line or Column, then the numbers 1, 2, 3, … are used as x-values to calculate the trend line. For such charts the XY chart type might be more suitable.

1. To insert a trend line for a data series, first double-click the chart to enter edit mode and select the data series in the chart to which a trend line is to be created.

2. Choose Insert - Trend Line, or right-click the data series to open the context menu, and choose Insert Trend Line.

3. Mean Value Lines are special trend lines that show the mean value. Use Insert - Mean Value Lines to insert mean value lines for data series.

4. To delete a trend line or mean value line, click the line, then press the Del key.

The menu item Insert - Trend Line is only available when the chart is in edit mode. It will appear grayed out if the chart is in edit mode but no data series is selected.

Đường xu hướng có cùng màu với chuỗi dữ liệu tương ứng. Để thay đổi các thuộc tính của đường, lựa chọn đường xu hướng rồi chọn lệnh Định dạng > Định dạng vùng chọn > Đường.

A trend line is shown in the legend automatically. Its name can be defined in options of the trend line.

## Trend Line Equation and Coefficient of Determination

When the chart is in edit mode, LibreOffice gives you the equation of the trend line and the coefficient of determination R2, even if they are not shown: click on the trend line to see the information in the status bar.

To show the trend line equation, select the trend line in the chart, right-click to open the context menu, and choose Insert Trend Line Equation.

To change format of values (use less significant digits or scientific notation), select the equation in the chart, right-click to open the context menu, and choose Format Trend Line Equation - Numbers.

Default equation uses x for abscissa variable, and f(x) for ordinate variable. To change these names, select the trend line, choose Format - Format Selection – Type and enter names in X Variable Name and Y Variable Name edit boxes.

To show the coefficient of determination R2, select the equation in the chart, right-click to open the context menu, and choose Insert R2.

If intercept is forced, coefficient of determination R2 is not calculated in the same way as with free intercept. R2 values can not be compared with forced or free intercept.

## Trend Lines Curve Types

The following regression types are available:

- Linear trend line: regression through equation y=a∙x+b. Intercept b can be forced.

- Polynomial trend line: regression through equation y=Σi(ai∙xi). Intercept a0 can be forced. Degree of polynomial must be given (at least 2).

- Logarithmic trend line: regression through equation y=a∙ln(x)+b.

- Exponential trend line: regression through equation y=b∙exp(a∙x).This equation is equivalent to y=b∙mx with m=exp(a). Intercept b can be forced.

- Power trend line: regression through equation y=b∙xa.

- Moving average trend line: simple moving average is calculated with the n previous y-values, n being the period. No equation is available for this trend line.

## Ràng buộc

Phép tính đường xu hướng chỉ nhận ra đôi dữ liệu có giá trị này:

- Logarithmic trend line: only positive x-values are considered.

- Exponential trend line: only positive y-values are considered, except if all y-values are negative: regression will then follow equation y=-b∙exp(a∙x).

- Power trend line: only positive x-values are considered; only positive y-values are considered, except if all y-values are negative: regression will then follow equation y=-b∙xa.

Khuyên bạn chuyển dạng dữ liệu cho phụ hợp: tốt nhất khi làm việc với bản sao của dữ liệu gốc, và chuyển dạng dữ liệu đã sao chép.

## Calculate Parameters in Calc

Bạn cũng có thể tính các tham số dùng hàm Calc như theo đây.

### Phương trình hồi quy tuyến tính

Hồi quy tuyến tính theo phương trình y=m*x+b.

m = SLOPE(Dữ_liệu_Y;Dữ_liệu_X)

b = INTERCEPT(Dữ_liệu_Y ;Dữ_liệu_X)

Tính hệ số định trị bằng

r2 = RSQ(Data_Y;Data_X)

Besides m, b and r2 the array function LINEST provides additional statistics for a regression analysis.

### The logarithmic regression equation

The logarithmic regression follows the equation y=a*ln(x)+b.

a = SLOPE(Dữ_liệu_Y;LN(Dữ_liệu_X))

b = INTERCEPT(Dữ_liệu_Y ;LN(Dữ_liệu_X))

r2 = RSQ(Data_Y;LN(Data_X))

### Phương trình hồi quy số mũ

Đối với đường cong hồi quy số mũ thì chuyển dạng sang mô hình tuyến tính. Hàm vừa khít đường cong tối ưu cân xứng với mô hình tuyến tính, và kết quả được giải thích cho phù hợp.

The exponential regression follows the equation y=b*exp(a*x) or y=b*mx, which is transformed to ln(y)=ln(b)+a*x or ln(y)=ln(b)+ln(m)*x respectively.

a = SLOPE(LN(Dữ_liệu_Y);Dữ_liệu_X)

Giá trị cho biến thể thứ hai được tính như theo :

m = EXP(SLOPE(LN(Dữ_liệu_Y);Dữ_liệu_X))

b = EXP(INTERCEPT(LN(Dữ_liệu_Y);Dữ_liệu_X))

Tính hệ số định trị bằng

r2 = RSQ(LN(Data_Y);Data_X)

Besides m, b and r2 the array function LOGEST provides additional statistics for a regression analysis.

### Phương trình hồi quy lũy thừa

For power regression curves a transformation to a linear model takes place. The power regression follows the equation y=b*xa, which is transformed to ln(y)=ln(b)+a*ln(x).

a = SLOPE(LN(Dữ_liệu_Y);LN(Dữ_liệu_X))

b = EXP(INTERCEPT(LN(Dữ_liệu_Y);LN(Dữ_liệu_X))

r2 = RSQ(LN(Data_Y);LN(Data_X))

### Phương trình hồi quy đa thức

For polynomial regression curves a transformation to a linear model takes place.

Create a table with the columns x, x2, x3, … , xn, y up to the desired degree n.

Use the formula =LINEST(Data_Y,Data_X) with the complete range x to xn (without headings) as Data_X.

The first row of the LINEST output contains the coefficients of the regression polynomial, with the coefficient of xn at the leftmost position.

The first element of the third row of the LINEST output is the value of r2. See the LINEST function for details on proper use and an explanation of the other output parameters.

Chủ đề Liên quan

X/Y Error Bars

LINEST function

LOGEST function

SLOPE function

INTERCEPT function

RSQ function

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