title: Very high residual Sum-of-Squares
body: <p>I'm having a problem with the square sum-of-residues of an fitting. The square sum of the residues is too high which indicates that the fit is not very good. However, visually it looks fine to have this very high residual value ... Can anyone help me to know what's going on?</p>
  
  <p>My data:</p>
  
  <pre><code>x=c(0.017359, 0.019206, 0.020619, 0.021022, 0.021793, 0.022366, 0.025691, 0.025780, 0.026355, 0.028858, 0.029766, 0.029967, 0.030241, 0.032216, 0.033657,
   0.036250, 0.039145, 0.040682, 0.042334, 0.043747, 0.044165, 0.044630, 0.046045, 0.048138, 0.050813, 0.050955, 0.051910, 0.053042, 0.054853, 0.056886,
  0.058651, 0.059472, 0.063770,0.064567, 0.067415, 0.067802, 0.068995, 0.070742,0.073486, 0.074085 ,0.074452, 0.075224, 0.075853, 0.076192, 0.077002,
   0.078273, 0.079376, 0.083269, 0.085902, 0.087619, 0.089867, 0.092606, 0.095944, 0.096327, 0.097019, 0.098444, 0.098868, 0.098874, 0.102027, 0.103296,
   0.107682, 0.108392, 0.108719, 0.109184, 0.109623, 0.118844, 0.124023, 0.124244, 0.129600, 0.130892, 0.136721, 0.137456, 0.147343, 0.149027, 0.152818,
  0.155706,0.157650, 0.161060, 0.162594, 0.162950, 0.165031, 0.165408, 0.166680, 0.167727, 0.172882, 0.173264, 0.174552,0.176073, 0.185649, 0.194492,
   0.196429, 0.200050, 0.208890, 0.209826, 0.213685, 0.219189, 0.221417, 0.222662, 0.230860, 0.234654, 0.235211, 0.241819, 0.247527, 0.251528, 0.253664,
   0.256740, 0.261723, 0.274585, 0.278340, 0.281521, 0.282332, 0.286166, 0.288103, 0.292959, 0.295201, 0.309456, 0.312158, 0.314132, 0.319906, 0.319924,
   0.322073, 0.325427, 0.328132, 0.333029, 0.334915, 0.342098, 0.345899, 0.345936, 0.350355, 0.355015, 0.355123, 0.356335, 0.364257, 0.371180, 0.375171,
  0.377743, 0.383944, 0.388606, 0.390111, 0.395080, 0.398209, 0.409784, 0.410324, 0.424782 )
  
  
  y= c(34843.40, 30362.66, 27991.80 ,28511.38, 28004.74, 27987.13, 22272.41, 23171.71, 23180.03, 20173.79, 19751.84, 20266.26, 20666.72, 18884.42, 17920.78, 15980.99, 14161.08, 13534.40, 12889.18, 12436.11,
  12560.56, 12651.65, 12216.11, 11479.18, 10573.22, 10783.99, 10650.71, 10449.87, 10003.68,  9517.94,  9157.04,  9104.01,  8090.20,  8059.60,  7547.20,  7613.51,  7499.47,  7273.46,  6870.20,  6887.01,
  6945.55,  6927.43,  6934.73,  6993.73,  6965.39,  6855.37,  6777.16,  6259.28,  5976.27,  5835.58,  5633.88,  5387.19,  5094.94,  5129.89,  5131.42,  5056.08,  5084.47,  5155.40,  4909.01,  4854.71,
  4527.62,  4528.10,  4560.14,  4580.10,  4601.70,  3964.90,  3686.20,  3718.46,  3459.13,  3432.05,  3183.09,  3186.18,  2805.15,  2773.65,  2667.73,  2598.55,  2563.02,  2482.63,  2462.49,  2478.10,
  2441.70,  2456.16,  2444.00,  2438.47,  2318.64,  2331.75,  2320.43,  2303.10,  2091.95,  1924.55, 1904.91,  1854.07,  1716.52,  1717.12,  1671.00,  1602.70,  1584.89,  1581.34,  1484.16,  1449.26,
  1455.06,  1388.60,  1336.71,  1305.60,  1294.58,  1274.36,  1236.51,  1132.67,  1111.35,  1095.21,  1097.71,  1077.05,  1071.04,  1043.99,  1036.22,   950.26,   941.06,   936.37,   909.72,   916.45,
  911.01, 898.94,   890.68,   870.99,   867.45,   837.39,   824.93,   830.61,   815.49,   799.77,   804.84,   804.88,   775.53,   751.95,   741.01,   735.86,   717.03,   704.57,   703.74,   690.63,
  684.24,   650.30,   652.74,   612.95 )
  </code></pre>
  
  <p>Then make fit using the nlsLM function (minpack.lm package):</p>
  
  <pre><code>library(magicaxis)
  library(minpack.lm)
  
  sig.backg=3*10^(-3) 
  
  mod &lt;- nlsLM(y ~ a *( 1 + (x/b)^2 )^c+sig.backg,
               start = c(a = 0, b = 1, c = 0),
               trace = TRUE)
  
  ## plot data
  magplot(x, y, main = "data", log = "xy", pch=16)
  ## plot fitted values
  lines(x, fitted(mod), col = 2, lwd = 4 )
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/saCaJ.png" alt="plot: points and fitting"></p>
  
  <p>This value is the residue:</p>
  
  <pre><code>&gt; print(mod)
  Nonlinear regression model
    model: y ~ a * (1 + (x/b)^2)^c + sig.backg
     data: parent.frame()
           a          b          c 
  68504.2013     0.0122    -0.6324 
   residual sum-of-squares: 12641435
  
  Number of iterations to convergence: 34 
  Achieved convergence tolerance: 0.0000000149
  </code></pre>
  
  <p>sum-of-squares residual is too high : 12641435 ...</p>
  
  <p>Is that so or is something wrong with the adjustment? It is bad?</p>