  In this paper, we have investigated an anisotropic cosmological model in
$f(Q)$ gravity with string fluid in LRS Bianchi type-I universe. We have
considered the arbitrary function $f(Q)=Q+\alpha\sqrt{~Q}+2\Lambda$ where
$\alpha$ is model free parameter and $\Lambda$ is the cosmological constant. We
have established a relationship between matter energy density parameter
$\Omega_{m}$ and dark energy density parameter $\Omega_{\Lambda}$ through
Hubble function using using constant equation of state parameter $\omega$. We
have made observational constraint on the model using $\chi^2$-test with
observed Hubble datasets $H(z)$ and SNe Ia datasets, and obtained the best fit
values of cosmological parameters. We have used these best fit values in the
result and discussion. We have discussed our result with cosmographic
coefficients and found a transit phase dark energy model. Also, we analyzed the
Om diagnostic function for anisotropic universe and found that our model is
quintessence dark energy model.
