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Getting differnet answers fromMatlab for what looks like the same expression
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I am trying to raise a real number (or vector of real numbers) to a fractional power.
V = -10:0.1:80;
V0 = 8;
m = 0.323;
Vx = (1 + V/V0);
Vx(1)
ans =
-0.25
>> sprintf('%0.55f', Vx(1))
ans =
'-0.2500000000000000000000000000000000000000000000000000000'
>> (Vx(1))^.323
ans =
0.337319506343289 + 0.542770712359585i
sprintf('%0.55f', -0.25)
ans =
'-0.2500000000000000000000000000000000000000000000000000000'
>> -0.25^.323
ans =
-0.6390
Why is the power of one version of 0.25 real, and the other is complex, when both versions of "-0.25" are identical to 55 sf?
0 个评论
回答(1 个)
Fangjun Jiang
2020-3-9
Try this and hope you know why
(-0.25)^.323
2 个评论
Steven Lord
2020-3-9
To be more explicit, the power and matrix power operators (.^ and ^ respectively) have higher precedence (level 2) than unary minus (the unary - operator) has (level 4.) See this page for the precedence breakdown. Parentheses are at level 1, which is why Fangjun Jiang's suggestion gives a complex result.
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