Why do I get "Array indices must be positive integers or logical values"

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maria serey-roman
maria serey-roman 2019-4-25
编辑： Walter Roberson 2019-4-25
Very new at matlab, i'm trying to fit linear function to a set of values. I keep getting "Array indices must be positive integers or logical values"
Please advise.
x = [62857 63320 63202 64754 64109 64298]'; % Population
y = [16366669 16864938 17087795 17224537 17301839 17095073]'; % Ridership
n = numel(y); % number of points being fitted
plot(x,y, '+')
A = [ones(6,1), x]; % design matrix
m = size(A,2); % parameters that we want fitted
b = A \ y;
f(x) = b(1) + b(2) *x;
xi = linspace(0,100);
fxi = f(xi);
plot(x, y, '+', xi, fxi)

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采纳的回答

Mauro Fusco
Mauro Fusco 2019-4-25
Arrays in Matlab are indexed starting from 1. Just replace xi = linspace(0,100); with
xi = linspace(1,100);
and it will not give error.

更多回答（1 个）

Walter Roberson
Walter Roberson 2019-4-25
编辑：Walter Roberson 2019-4-25
Please read https://www.mathworks.com/matlabcentral/answers/453477-error-array-indices-must-have-positive-or-logical-values#answer_368263 : you are confusing formula and expressions.
Also, your x range is about 60000, but the range over which you plot the projected line is 0 to 100.
plot(x, y, '+', x, polyval(flipud(b), x))

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