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0
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1 function yhat=spence21(y)
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2 % function for Spencer's 21-point graduation rule.
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3 % set out following Spencer's hand-calculation method,
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4 % which isn't the shortest computer program!
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5
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6 oten = ones(10,1);
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7 n = length(y);
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8 y = [ oten*y(1); y; oten*y(n) ];
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9
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10 n = length(y);
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11 k = 4:(n-3);
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12 y1 = -y(k-3) + y(k-1) + 2*y(k) + y(k+1) -y(k+3);
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13
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14 n = length(y1);
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15 k = 4:(n-3);
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16 y2 = y1(k-3)+y1(k-2)+y1(k-1)+y1(k)+y1(k+1)+y1(k+2)+y1(k+3);
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17
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18 n = length(y2);
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19 k = 3:(n-2);
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20 y3 = y2(k-2)+y2(k-1)+y2(k)+y2(k+1)+y2(k+2);
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21
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22 n = length(y3);
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23 k = 3:(n-2);
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24 y4 = y3(k-2)+y3(k-1)+y3(k)+y3(k+1)+y3(k+2);
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25
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26 yhat = y4/350;
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27 return;
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