how to calculate the slope of a line?

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Amr Hashem
Amr Hashem 2015-8-18
评论： Amr Hashem 2015-8-19
I have a data A,B and I want to calculate the slope between two existing points
I want to find the slop between 2012 & 2013 points I try:
A=[ 234228; 249150 ; 265021 ;281904 ;299862 ];
B=[ 7380; 8045 ; 9903 ;15058 ;13610 ];
plot(A,B);
a = [2010:2014]'; b = num2str(a); c = cellstr(b);
dx = 1; dy = 1; % displacement so the text does not overlay the data points
text(A+dx, B+dy , c)
hold on
coefficients = polyfit(A, B, 1);
slope = coefficients(1);
text(266000,11500,num2str(slope,'y = %.3fx'))
but it seems to be wrong :( ANY IDEA

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采纳的回答

Star Strider
Star Strider 2015-8-18
编辑：Star Strider 2015-8-18
The easiest way is to use the diff funciton. This puts the 2012-2013 slope as the third one in the series:
SlopeBetweenPoints = diff(B)./diff(A)
Slope_2012_2013 = SlopeBetweenPoints(3)
SlopeBetweenPoints =
44.5651e-003
117.0689e-003
305.3367e-003
-80.6326e-003
Slope_2012_2013 =
305.3367e-003
EDIT — To print a table:
fprintf(1, '\nSlopes:\n')
fprintf(1, '\t%4d-%4d\t% .4f\n', [a(1:end-1), a(2:end), SlopeBetweenPoints]')
Slopes:
2010-2011 0.0446
2011-2012 0.1171
2012-2013 0.3053
2013-2014 -0.0806

更多回答（1 个）

John D'Errico
John D'Errico 2015-8-18
编辑：John D'Errico 2015-8-18
The slope between consecutive points is simple.
slopes = diff(B)./diff(A);
Pick whatever slope you want from the result. So, here:
A=[ 234228; 249150 ; 265021 ;281904 ;299862 ];
B=[ 7380; 8045 ; 9903 ;15058 ;13610 ];
slopes = diff(B)./diff(A)
slopes =
0.044565
0.11707
0.30534
-0.080633
slopes(3)
ans =
0.30534

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