## General Question

# How do I produce a line of best fit for graphs when I know the function they are supposed to map to?

Hello, I am currently writing up my laboratory report and I am stuck on what to do with my graphs. At the moment I have just produced a scatter graph, but I want to include a line of best fit so I can find which value corresponds to the 75% threshold.

The lines are supposed to map towards this equation:

Y = 100.0—(50.0*(2.0^(-((X/A)^B))))

However when running Opcode (which runs bootstraps in order to match the values in my graph to that equation) failed in all attempts.

I am using excel, but wouldn’t mind downloading something free in order to do the lines of best fits. If anyone could recommend some simple software I can use, I would be grateful. At the moment I am just using MS Excel which i’m not sure if the trend lines are valid (nor which one I am supposed to use).

P.S. The equation given should produce something that looks like:

http://www.nature.com/neuro/journal/v8/n1/extref/nn1373-S2.gif

Problems are that my graphs all look different: the first two appear to be around random and the rest look curved but barely anything like that.

If you need any more information, please ask as I am not sure what I need to give.

Thanks.

Appendix: The results of the 5 conditions (values of Y, X axis = 0.002 to 0.02; increasement of 0.002; 10 values total).

51.333

43.667

61.349

64.000

64.667

58.167

49.778

66.333

48.762

62.952

54.814

43.286

61.000

33.944

48.429

52.500

65.333

58.750

57.545

52.762

33.500

37.381

39.952

61.667

41.333

47.500

42.000

54.833

85.143

87.143

50.000

48.500

39.127

45.000

59.000

35.556

63.333

70.556

88.000

95.000

56.095

74.762

78.667

86.786

100.000

96.000

92.626

96.364

100.000

100.000

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