Trendlinjer
Trend lines can be added to all 2D chart types except for Pie and Stock 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.
-
To insert a trend line for a data series, select the data series in the chart. Choose
, or right-click to open the context menu, and choose . -
Mean Value Lines are special trend lines that show the mean value. Use
to insert mean value lines for data series. -
To delete a trend line or mean value line, click the line, then press the Del key.
A trend line is shown in the legend automatically. Its name can be defined in options of the trend line.
Trendlinjen har samma fÀrg som motsvarande dataserie. Du Àndrar linjeegenskaperna genom att markera trendlinjen och vÀlja
.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 .
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
.Default equation uses x for abscissa variable, and f(x) for ordinate variable. To change these names, select the trend line, choose 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
.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=aâx+b. Intercept b can be forced.
-
Polynomial trend line: regression through equation y=ÎŁi(aiâxi). Intercept a0 can be forced. Degree of polynomial must be given (at least 2).
-
Logarithmic trend line: regression through equation y=aâln(x)+b.
-
Exponential trend line: regression through equation y=bâexp(aâx).This equation is equivalent to y=bâmx with m=exp(a). Intercept b can be forced.
-
Power trend line: regression through equation y=bâxa.
-
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.
BegrÀnsningar
I berÀkningen av en trendlinje medtas endast datapar med följande vÀrden:
-
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=-bâexp(aâx).
-
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=-bâxa.
Du bör omvandla data i enlighet med det. Det Àr bÀst att arbeta med en kopia av originaldata och omvandla kopierad data.
Calculate Parameters in Calc
Du kan Àven berÀkna parametrar med Calc-funktioner enligt följande.
LinjÀr regressionsekvation
DenlinjÀra regression följer ekvationen y=m*x+b.
m = SLOPE(Data_Y;Data_X)
b = INTERCEPT(Data_Y ;Data_X)
BerÀkna koefficienten genom bestÀmning av
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(Data_Y;LN(Data_X))
b = INTERCEPT(Data_Y ;LN(Data_X))
r2 = RSQ(Data_Y;LN(Data_X))
Exponentiell regressionsekvation
För exponentiella regressionskurvor sker en omvandling till en linjÀr modell. Den optimala kurvanpassningen Àr relaterad till den linjÀra modellen och resultaten tolkas dÀrefter.
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(Data_Y);Data_X)
Variabler för den andra variationen berÀknas pÄ följande sÀtt:
m = EXP(SLOPE(LN(Data_Y);Data_X))
b = EXP(INTERCEPT(LN(Data_Y);Data_X))
BerÀkna koefficienten genom bestÀmning av
r2 = RSQ(LN(Data_Y);Data_X)
Besides m, b and r2 the array function LOGEST provides additional statistics for a regression analysis.
Potentiell regressionsekvation
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(Data_Y);LN(Data_X))
b = EXP(INTERCEPT(LN(Data_Y);LN(Data_X))
r2 = RSQ(LN(Data_Y);LN(Data_X))
Polynom regressionsekvation
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.