MATLAB: How to find fifth value after somewhere in a series OR the end of the series, whichever comes first

endfindfirstmaxminrange

I have a set of data for which I want to find the minimum, then take a range from 5 values either side of this. I have done this using the following:

xrangemin=xdata(find(xdata==xdata(ydata==min(ydata))-5):find(xdata==xdata(ydata==min(ydata))+5));

This works, UNLESS the min(ydata) is within 5 values of either end of dataset, in which case it returns [](0x1).

Is there a way to say to matlab 'find the fifth value before\after this one OR the first/last one whichever you find first'?

Thanks very much

Best Answer

you can add max from 1 and 5 before the min and the min from end and 5 after the min.

    xrangemin=xdata(max(1,find(xdata==xdata(ydata==min(ydata))-5)):min(end,find(xdata==xdata(ydata==min(ydata))+5));

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By using roots() on symbolic variables, you can get four closed form expressions for the roots. They occur in pairs, A+/-B and P+/-Q where B and Q are sqrt(), so by detecting whether the sqrt() involve imaginary quantities you can eliminate conjugate pairs as you wanted.

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t2 = C2.*3.0;
t3 = C3.*2.0;
t4 = C4.*2.0;
t5 = C5.*3.0;
t9 = 1.0./C5;
t13 = sqrt(3.0);
t14 = sqrt(6.0);
t6 = -t3;
t7 = -t4;
t8 = -t5;
t10 = t9.^2;
t11 = t9.^3;
t15 = C2.*t9;
t12 = t10.^2;
t16 = C1+C6+t6;
t17 = C1+C6+t7;
t18 = t15.*1.2e+1;
t19 = t2+t8;
t20 = -t18;
t21 = t17.^2;
t22 = t17.^3;
t24 = t9.*t16;
t25 = t9.*t19;
t26 = (t9.*t17)./4.0;
t32 = t10.*t16.*t17.*3.0;
t35 = (t10.*t16.*t17)./4.0;
t37 = (t10.*t17.*t19)./2.0;
t23 = t21.^2;
t27 = t10.*t21.*(3.0./8.0);
t28 = (t11.*t22)./8.0;
t36 = -t35;
t38 = t11.*t19.*t21.*(3.0./4.0);
t39 = (t11.*t19.*t21)./1.6e+1;
t29 = -t27;
t30 = -t28;
t31 = t12.*t23.*(3.0./2.56e+2);
t33 = t12.*t23.*(9.0./6.4e+1);
t40 = -t39;
t34 = -t33;
t41 = t25+t29;
t47 = t24+t30+t37;
t53 = t15+t31+t36+t40;
t42 = t41.^2;
t43 = t41.^3;
t48 = t47.^2;
t54 = t53.^2;
t55 = t53.^3;
t58 = t41.*t53.*(4.0./3.0);
t59 = t41.*t53.*7.2e+1;
t44 = t42.^2;
t45 = t43.*2.0;
t46 = t43./2.7e+1;
t49 = t48.^2;
t50 = t48.*2.7e+1;
t52 = t48./2.0;
t56 = t55.*2.56e+2;
t57 = t43.*t48.*4.0;
t61 = t42.*t54.*1.28e+2;
t62 = t41.*t48.*t53.*1.44e+2;
t51 = t49.*2.7e+1;
t60 = t44.*t53.*1.6e+1;
t63 = t51+t56+t57+t60+t61+t62;
t64 = sqrt(t63);
t65 = t13.*t64.*3.0;
t66 = (t13.*t64)./1.8e+1;
t67 = t45+t50+t59+t65;
t69 = t46+t52+t58+t66;
t68 = sqrt(t67);
t70 = t69.^(1.0./3.0);
t72 = 1.0./t69.^(1.0./6.0);
t71 = t70.^2;
t74 = t41.*t70.*6.0;
t76 = t14.*t47.*t68.*3.0;
t73 = t71.*9.0;
t75 = -t74;
t77 = -t76;
t78 = t20+t32+t34+t38+t42+t73+t75;
t79 = sqrt(t78);
t80 = 1.0./t78.^(1.0./4.0);
t81 = t42.*t79;
t83 = t53.*t79.*1.2e+1;
t84 = t73.*t79;
t85 = t71.*t79.*-9.0;
t86 = (t72.*t79)./6.0;
t88 = t41.*t70.*t79.*1.2e+1;
t82 = -t81;
t87 = -t86;
t89 = -t88;
t90 = t76+t82+t83+t85+t89;
t91 = t77+t82+t83+t85+t89;
t92 = sqrt(t90);
t93 = sqrt(t91);
t94 = (t72.*t80.*t92)./6.0;
t95 = (t72.*t80.*t93)./6.0;
GG = [t26+t87-t94; t26+t87+t94; t26+t86-t95; t26+t86+t95];

Best Answer

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