portfolio.optim(x, pm = mean(x), riskless = FALSE,
                shorts = TRUE, rf = 0.0, reslow = NULL, reshigh = NULL,
                covmat = cov(x))

reslow和reshigh是投资组合权重约束的话，假设我希望每个投资的权重在-0.1到0.1之间，该如何赋值呢？我尝试reslow=-0.1，reshigh=0.1之后结果如下：
reslow has not the right dimension
请大神指点