Problems in fitting the experimental data with the expression

• To: mathgroup at smc.vnet.net
• Subject: [mg99842] Problems in fitting the experimental data with the expression
• From: umamaheswari1973 at gmail.com
• Date: Sat, 16 May 2009 05:19:03 -0400 (EDT)

```My exp data x-values are
ax = expdata[[All, 1]]
{600.58, 598.2, 595.81, 593.43, 591.04, 588.66, 586.27, 583.88, \
581.49, 579.1, 576.71, 574.32, 571.93, 569.54, 567.15, 564.76, \
562.36, 559.97, 557.58, 555.18, 552.79, 550.39, 547.99, 545.6, 543.2,
\
540.8, 538.4, 536, 533.6, 531.2, 528.79, 526.39, 523.99, 521.58, \
519.18, 516.77, 514.37, 511.96, 509.55, 507.15, 504.74, 502.33, \
499.92, 497.51, 495.1, 492.69, 490.27, 487.86, 485.45, 483.03, \
480.62, 478.2, 475.79, 473.37, 470.95, 468.54, 466.12, 463.7, 461.28,
\
458.86, 456.44, 454.01, 451.59, 449.17, 446.75, 444.32, 441.9, \
439.47, 437.04, 434.62, 432.19, 429.76, 427.33, 424.9, 422.47, \
420.04, 417.61, 415.18, 412.75, 410.31, 407.88, 405.44, 403.01, \
400.57}

y-datas are

ay = expdata[[All, 2]]
{241.27, 241.5, 241.8, 246.63, 243.53, 242.6, 242.53, 242.03, 243.57,
\
242.57, 240.4, 242.33, 240.27, 239.37, 239.3, 236.73, 237.07, 240.17,
\
238.6, 241.53, 238.07, 243.47, 240.3, 241.8, 244.73, 244.67, 246.9, \
252.53, 257.67, 263.77, 275.23, 291.53, 335.87, 438.13, 563.43, 527, \
437.7, 405.73, 414.07, 426.1, 451.97, 479.97, 511.9, 552.8, 592.97, \
619.57, 644.3, 645.07, 635.07, 602, 569.2, 520.17, 472.13, 436.83, \
404.53, 384.13, 366.23, 350.73, 337.57, 325.67, 314.47, 307.77, \
301.4, 295.13, 289.53, 288.03, 284.37, 274.6, 272.8, 269.2, 265.8, \
263.7, 261.87, 262.87, 259.43, 261.07, 262.57, 264.97, 262.1, 263.5, \
265.13, 261, 259.03, 264.43}

fw[w_?NumericQ, L_?NumericQ] :=
NIntegrate[
4*Pi*q^2*Exp[-(L^2*q^2)/(16*
Pi^2)]/((w - (520 - (120*(q/1.15712)^2)))^2 + (3.5/2)^2), {q,
a, b}]

I want to  fit the value of L.

w : values are taken from the x-data of the experiment.

FindFit[ay, fw[w, L], {L}, {ax[[1]], ax[[84]]}]

I got the error as

General::ivar: 600.58` is not a valid variable. >>

I don't know how to solve this problem of fitting the value of L with
the experimental data.

Kindly do the needful to solve this

```

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