clf;
L = 100;
R = 10;

Q = 0.01:0.01:0.25;

P = [ .9711328425
      .8911140861
      .7773005408
      .6517422571
      .5341179156
      .4366139453

                                   .3624762674

                                   .3080820363

                                   .2668503402

                                   .2328624921

                                   .2027402701

                                   .1755647348

                                   .1516401730

                                   .1312210554

                                   .1139354974

                                  .09896470630

                                  .08555056350

                                  .07334271221

                                  .06237339004

                                  .05278194946

                                  .04455935030

                                  .03749433554

                                  .03130459339

                                  .02580115513

                                  .02094713772
];

plot(Q.*Q, log(Q.*P'), 'o');
hold on;
plot(Q.*Q, log(Q.* (pi*exp(-Q.*Q*R*R/4)./Q/L)));

xlabel ('(Q*Angstrom)^2       dot: exact(eq.1)  line: approximate(eq.2)');
ylabel ('log(Q*P(Q)');
title ('Structure factor of a randomly oriented cylinder with L = 100 A, R = 10 A');

